How to name amines. General formula of amines

Every amine has a lone pair of electrons on its nitrogen atom. When an amine enters water, protons from water can form a new covalent polar bond with the nitrogen atom by the donor-acceptor mechanism, thus giving an alkyl- or arylammonium ion. Water that has lost a proton turns into a hydroxide ion. The environment becomes alkaline. Thus amines are bases. The strength of these bases depends on the nature and number of radicals associated with nitrogen. Aliphatic radicals, such as methyl, ethyl, etc., showing their electron-donor properties, increase the basicity of amines. Aromatic radicals, on the contrary, greatly reduce the basicity due to the delocalization of a pair of electrons along the benzene ring. According to Linus Pauling's resonance theory, it looks like this:

As can be seen, the lone pair of electrons is present on the nitrogen atom only in one of the resonant structures (mesomeric forms). In three other bipolar structures on the nitrogen atom, on the contrary, there is a “+” charge, which naturally prevents protonation. This is the reason for the sharp decrease in basicity. Availability in O- And P- positions of negative charges allows us to suggest that it is easy for electrophilic substitution reactions to proceed exactly to these positions, where the attacking particle is a cation (for example,

) Examples of reactions of this type with aromatic amines will be given below.

Quantitatively, the strength of the bases is characterized by the values ​​of K b or their negative logarithms pK b. The index "b" means that we are talking about the equilibrium constant between the base - base, which is the amine and its conjugate acid, that is, the ammonium ion:

By definition, such a reversible reaction is described by the analytical expression:

Since the concentration of water in dilute aqueous solutions is practically constant and equal to 55.5 mol/l, then it is introduced into the “new” equilibrium constant:

Multiplying the numerator and denominator of the right side of the equation by [Н + ] and taking into account that [Н + ] [OH - ] = K w = 10 -14 we get:

Taking the logarithm of this analytic expression using decimal logarithms,

we come to the equation:

Reversing the signs and introducing the generally accepted notation: - lg = p, we get:

Since the logarithm of a unit for any base is equal to zero, and 14 - pH \u003d pOH, it is obvious that pK b corresponds to the value of the concentration of hydroxyl ions at which half of the ammonium cations will pass with the elimination of a proton into a free amine. The pK b value for bases is the same as the pK a value for acids. Below is a table, the data of which show the influence of the nature of the radicals and their number on the values ​​of the basicity constants of various amines.

Foundation name	Base Formula	Base type	K b at 25 o C	The value of pK b at 25 ° C
Ammonia			1,75 10 -5	4,75
methylamine		Primary aliphate.	4,60 10 - 4	3,34
ethylamine		Primary aliphate.	6,50 10 - 4	3,19
Butylamine		Primary aliphate.	4,00 10 - 4	3,40
Isobutiamine		Primary aliphate.	2,70 10 - 4	3,57
Deut-butylamine		Primary aliphate.	3,60 10 - 4	3,44
Tret-butylamine		Primary aliphate.	2,80 10 - 4	3,55
benzylamine		Primary aliphate.	2,10 10 -5	4,67
Dimethylamine		Secondary aliphate.	5,40 10 -4	3,27
diethylamine		Secondary aliphate.	1,20 10 - 3	2,91
Trimethylamine		Tertiary aliphate.	6,50 10 -5	4,19
Triethylamine		Tertiary aliphate.	1,00 10 - 3	3,00
Aniline		Primary aroma.	4,30 10 - 10	9,37
P-toluidine		Primary aroma.	1,32 10 -9	8,88
P-nitroaniline		Primary aroma.	1,00 10 - 13	13,0
N,N-dimethylaniline		Tertiary fatty aromatic	1,40 10 -9	8,85
Diphenylamine		Secondary aroma.	6,20 10 -14	13,21
pyridine		Heteroaromatic	1,50 10 - 9	8,82
Quinoline		Heteroaromatic	8,70 10 -10	9,06
Piperidine		Secondary aliphate. and heterocyclic	1,33 10 -3	3,88
Hydrazine			9,30 10 -7	6,03
Hydroxylamine			8,90 10 - 9	8,05
ethanolamine		Prod. perv. alif.	1,80 10 - 5	4,75

The data in the table allow us to draw the following conclusions:

1) Aliphatic amines are much stronger bases than aromatic ones (about 100,000 - 1,000,000 times)

2) Heteroaromatic amines are similar in basicity to aromatic ones.

3) The basicity of aromatic amines is strongly influenced by substituents located in pair- position to the amino group. Electron-donating substituents increase the basicity of the amine, while electron-withdrawing substituents sharply lower it. The basicity ratio of aromatic amines containing methyl and nitro groups at the indicated position is approximately 10,000:1.

4) Secondary aliphatic amines are slightly more basic than primary ones, while tertiary ones have a basicity at the same level.

5) The nature of the radical in primary amines does not significantly affect the basicity of the amine.

6) Saturated heterocyclic amines have basicity at the level of secondary aliphatic amines.

7) Fatty aromatic amines have basicity at the level of aromatic amines.

8) Secondary aromatic amines have about 10,000 times less basicity than primary ones.

9) Electronegative atoms bound in the molecule to the nitrogen atom of the amino group lower its basicity by 10 (nitrogen) and 1000 times (oxygen).

10) An oxygen atom separated from the amino group by two methylene groups lowers its basicity by only 67 times.

It should also be noted that the basicity of acid amides due to the electron-withdrawing effect of the carbonyl group is very low - even lower than that of secondary aromatic amines: for acetamide pK b = 13.52; acetanilide pK b = 13.60 and urea pK b = 13.82

acetamide acetanilide urea

Like grounds primary, secondary and tertiary amines react with acids:

propylamine propylammonium bromide

dimethylamine dimethylammonium sulfate

trimethylamine trimethylammonium perchlorate

With polybasic acids can form not only medium, but and acid salts:

dimethylamine dimethylammonium hydrogen sulfate

methylisobutylamine methylisobutylammonium dihydroorthophosphate

Primary aromatic, and secondary and tertiary fatty aromatic amines with dilute aqueous solutions of strong acids also give salt:

Also able to form salt Under the influence concentrated strong acids, but at dilution with water these salts hydrolyzed, giving a weak base, that is starting amine:

Like very weak foundations, do not give salt neither with concentrated hydrochloric nor with sulfuric acids. True, triphenylamine still gives perchlorate with perchloric acid:

.

Primary aliphatic amines react in two stages: in the first, an extremely unstable in water even when cooled diazonium salt, which in the second stage reacts with water to form alcohol:

propylamine propyldiazonium chloride

propanol-1

In the reaction of a primary amine with sodium nitrite and hydrochloric acid, outgassing(bubbles are clearly visible) and fishy smell amine changes to alcohol is a qualitative reaction to a primary aliphatic amine.

If we sum up the two reactions above, we get:

Secondary amines react in a completely different way: under the action of sodium nitrite and hydrochloric acid, N-nitrosamine- very resistant even when heated connection:

methylethylamine N-nitrosomethylethiamin

In the reaction of a secondary aliphatic amine with sodium nitrite and hydrochloric acid, the formation of a yellow oil, poorly soluble in water and with an extremely unpleasant odor is a qualitative reaction to a secondary aliphatic amine.

Nitrosamines - carcinogens: regardless of the place and method of entry into the body of the experimental animal, they cause liver cancer. Widely used in experimental oncology. They act resorptively, that is, through the skin.

Tertiary aliphatic amines react from a mixture of sodium nitrite and hydrochloric acid only with acid:

There are no visible effects in this reaction. The smell subsides.

Primary aromatic amines react with the formation of relatively stable at temperatures from 0 to 5 o C diazonium salts. This reaction was first published in 1858 in a German chemistry journal by Peter Griess and bears his name:

The Griess reaction involves numerous aniline homologues containing alkyl substituents in o-,m- And P-position to the amino group:

It also includes aniline derivatives containing electron-acceptor, electron-donor substituents and substituents of a special group, for example:

With hydrobromic acid, the reaction is faster, but it is rarely used and only in the laboratory due to the high cost and scarcity of this acid.

In the production of salt, diazonium is immediately used to carry out the following stages of synthesis, but in the laboratory they are often isolated by an exchange reaction with a saturated solution of sodium tetrafluoroborate:

Diazonium salts are most often used to obtain numerous azo dyes by azo coupling with phenols (naphthols) and aromatic tertiary amines, for example:

The resulting azo dye is a pH indicator: in an acidic environment, due to the formation of a hydrogen bond, it has a flat structure in which the electron-donating effect of the hydroxyl group is weakened - this form is colored yellow. In the alkaline group, a proton breaks off from the hydroxyl group, a “phenolate ion” appears, which is the strongest ED substituent, and the color changes to red-orange:

The role of soda in the course of the azo coupling reaction is the binding of the resulting hydrochloric (or other strong) acid into an acid salt - sodium bicarbonate:

A mixture of sodium carbonate and bicarbonate is a buffer solution that creates a slightly alkaline environment.

With tertiary aromatic amines, azo coupling must take place in a slightly acidic medium, which is ensured by the addition of salts that hydrolyze at the anion, for example, sodium acetate. In a strongly acidic medium, the amine gives an ammonium salt, the cation of which naturally does not react with the diazonium cation.

Sodium acetate instantly reacts with the resulting hydrochloric acid. The result is a buffer solution consisting of weak acetic acid and excess sodium acetate. It provides a slightly acidic environment:

Secondary aromatic amines react with sodium nitrite and hydrochloric acid with education N-nitrosamines. For example, N-methylaniline gives N-nitroso-N-methylaniline - a yellow oil with an extremely unpleasant odor that solidifies at 13 ° C:

Aromatic N-nitrosoamines, like aliphatic ones, are carcinogens. They also cause liver cancer, and are also used in experimental oncology.

Aromatic N-nitrosoamines under the action of dry chloro- or hydrogen bromides or under the action of concentrated sulfuric acid undergo a rearrangement first published in 1886 in a German chemical journal by O. Fischer and E. Hepp. Under these conditions, the nitroso group is selectively transferred to P-position:

The resulting rearrangement of 4-nitroso-N-methylaniline has completely different physical properties and biological activity. It is a green solid with a melting point of 113°C. It fluoresces in solutions in organic solvents. It is not a carcinogen, however, it causes dermatitis.

Tertiary aromatic amines react with sodium nitrite and hydrochloric acid, Giving C-nitroso compounds. The nitroso group is selectively directed to P-position:

C-nitroso compounds are easily reduced by hydrogen on Raney nickel. In this case, unsymmetrical dialkyldiamines are obtained, for example:

Salts of aliphatic and aromatic amines can be easily converted back into amines by the action of alkalis, for example:

propylammonium perchlorate propylamine

methylpropylammonium hydrogen sulfate methylpropylamine

Quaternary ammonium bases, Conversely, they can be translated into quaternary ammonium salts action acids:

Dimethylethylisopropylammonium hydroxide Dimethylethylisopropylammonium chloride

As you can see, this is a common reaction of neutralizing an alkali with an acid - salt and water are obtained.

On page 19 of this manual, it was suggested that the reactions of electrophilic substitution in aromatic amines can easily occur in ortho- And pair- positions of the benzene nucleus. Indeed, aniline is easily brominated into all these positions at once:

N,N-dialkylanilines are sulfonated, nitrated, and diazotized in ortho- And pair-provisions:

With sodium acetate, a strong complex acid is converted into a weak one - acetic:

Application of amines

The simplest primary amine methylamine used in the synthesis of insecticides, fungicides, vulcanization accelerators, surface-active substances (surfactants), drugs, dyes, rocket fuels, solvents. For example, N-methyl-2-pyrrolidone, a popular solvent for varnishes and some dyes, is obtained by reacting methylamine with γ-butyrolactone (4-hydroxybutanoic acid cyclic ester):

γ-butyrolatone N-methyl-2-pyrrolidone

The simplest secondary amine dimethylamine used in the synthesis of insecticides, herbicides, vulcanization accelerators, surfactants, many drugs, dyes and important solvents such as dimethylforiamid (DMF), dimethylacetamide (DMAA) and hexamethylphosphotriamide (HMPTA) or hexametapol. DMF is produced in industry, for example, by reacting dimethylamine with formic acid methyl ester:

methyl formate dimethylamine DMF methanol

DMAA is produced industrially by reacting dimethylamine with acetic anhydride:

acetic anhydride DMAA

The industrial synthesis of hexametapol consists in the interaction of dimethylamine with phosphorus oxychloride:

phosphorus trichloride HMPTA

The simplest tertiary amine trimethylamine used in the synthesis of quaternary ammonium bases, flotation agents, retardants, feed additives. For example, the last step in the synthesis of carbacholine, a drug used in the treatment of glaucoma and postoperative atony of the intestine or bladder, is the interaction of trimethylamine with a carbamoyl derivative of ethylene chlorohydrin:

carbacholin

Cationic surfactants are obtained similarly:

trimethylalkylammonium chloride

ethylamine used in the production of dyes, surfactants, herbicides. For example, simazine, a herbicide for protecting corn and vegetables from weeds, is obtained by the interaction of ethylamine with the calculated amount of cyanuric chloride in an alkaline medium:

cyanuric chloride simazine

diethylamine used in the production of dyes, pesticides, rubber vulcanization accelerators, corrosion inhibitors, medicines, insect repellents. For example, a well-known mosquito repellent - DEET is obtained by the reaction:

acid chloride m-toluic acid N,N-diethyl- m-toluamide

Isopropylamine, butylamine, isobutylamine, second-butiamine and tert- butylamines used in similar industries.

1,6-hexanediamine widely used for the synthesis of nylon by the reaction of polycondensation with 1,4-butanedicarboxylic (adipic) acid:

Among drugs, many contain amino groups of various types. So, for example, out of 1308 drugs listed in the M.D. Mashkovsky, at least 70 are primary amines, at least 52 are secondary and at least 108 are tertiary. In addition, there are 41 quaternary ammonium salts and more than 70 amides of carboxylic acids, 26 amides of arylsulfonic acids and 12 amides of orthophosphoric acid derivatives among the drugs. There are also cyclic amides - lactams. There are 5 of them. Derivatives of natural amino acids - 14 items. The following are examples of medicinal products containing the listed functional groups:

Anestezin- ethyl ether P-aminobenzoic acid. It is a primary aromatic amine and an ester at the same time.

It has a local anesthetic effect. It is used to anesthetize wound and ulcerative surfaces, with vomiting of pregnant women, sea and air sickness.

Baclofen– 4-amino-3-( P-chloro)phenylbutanoic acid. It is a primary aliphatic amine, an ester and a halogen derivative of the benzene series at the same time.

Reduces muscle tension, has an analgesic effect. Used for multiple sclerosis.

Salbutamol – 2-tert-butylamino-1-(4"-hydroxy-3"-hydroxymethyl)phenylethanol. It is a secondary aliphatic amine, secondary and primary alcohols and phenol at the same time.

It has a bronchodilatory effect and prevents premature contractions in pregnant women. It is used for bronchial asthma and in obstetric practice.

Ortofen- sodium salt of 2-(2",6"-dichloro)phenylaminophenylacetic acid. It is a secondary aromatic amine, a salt of a carboxylic acid and a halogen derivative of the benzene series at the same time.

It has anti-inflammatory, analgesic and antipyretic effects. It is used for acute rheumatism, rheumatoid arthritis, Bechterew's disease, arthrosis, spondyloarthrosis.

Isoverin- N-isoamyl-1,5-pentanediamine dihydrochloride. It is a diammonium salt of primary and secondary amines simultaneously.

Lowers blood pressure, increases tone and enhances uterine muscle contractions. It is used as a labor accelerator and to stimulate uterine contractions in the postpartum period.

methylene blue- N,N,N',N'-tetramethylthionine chloride. It is both a tertiary fatty aromatic amine and an ammonium salt of the same amine. In addition, it contains a heteroaromatic ring with a "pyridine" nitrogen atom.

Applied externally as an antiseptic for burns, pyoderma and folliculitis. For cystitis and urethritis, the cavities are washed with a 0.02% blue solution.

Pentamine– 3-methyl-1,5-bis-(N,N-dimethyl-N-ethyl)ammonium-3-azapentane dibromide. It is both a tertiary aliphatic amine and a doubly quaternary ammonium salt of the same amines.

It has ganglioblocking activity. It is used for hypertensive crises, spasms of peripheral vessels, spasms of the intestines and biliary tract, renal colic, for the relief of acute attacks of bronchial asthma, with pulmonary and cerebral edema.

Nicotinamide- 3-pyridinecarboxylic acid amide. It is an amide of a carboxylic acid and a derivative of the nitrogen-containing heteroaromatic cycle - pyridine.

It has anti-pellagric properties, improves carbohydrate metabolism, has a positive effect in mild forms of diabetes, diseases of the liver, heart, gastric ulcer and duodenal ulcer. It is used for gastritis with low acidity, acute and chronic hepatitis, cirrhosis, spasms of the vessels of the extremities, kidneys and brain.

Sulfadimezin – 2-(P- aminobenzenesulfamido)-4,6-dimethylpyrimidine. Representative of a large group of sulfa drugs. It is simultaneously a sulfanilamide, a primary aromatic amine and a derivative of the nitrogen-containing heteroaromatic cycle - pyrimidine.

Like all drugs in this group, sulfadimezin is an active antimicrobial agent. It is used for pneumococcal, streptococcal, meningococcal infections, sepsis, gonorrhea, as well as infections caused by Escherichia coli and other microbes.

Fopurine - 6-diethyleneamidophosphamido-2-dimethylamino-7-methylpurine. It is simultaneously three times a phosphamide, a tertiary aromatic amine and a derivative of a nitrogen-containing heteroaromatic bicycle - purine

Hemodez- 6% aqueous-salt solution of low molecular weight polyvinylpyrrolidone. The elementary unit of the polymer contains a lactam ring.

Binds toxins circulating in the blood and quickly removes them through the renal barrier. Used for dysentery, dyspepsia, salmonellosis, burn disease in the phase of intoxication.

Histidine– L-β-imidazolylalanine or L-α-amino-β-(4-imidazolyl)propionic acid. It is an α-amino acid and a derivative of the nitrogen-containing heteroaromatic cycle - imidazole

Histidine is an essential amino acid; found in various organs, is part of carnosine, a nitrogenous extractive substance of muscles. In the body, it undergoes decarboxylation with the formation of histamine, one of the chemical factors (mediators) involved in the regulation of vital functions.

Angiotensinamide– L-asparaginyl-L-arginyl-L-valyl-L-tyrosinyl-L-valyl-L-histidinyl acetate – L-prolyl-L-phenylalanine. It is an acetic salt of an octapeptide consisting of natural α-amino acids.

In shock conditions, it is used for rapid and severe vasoconstriction of internal organs, skin, and kidneys. Angiotensinamide also has the ability to reduce the smooth muscles of the uterus, intestines, urinary and gallbladder. It stimulates the release of adrenaline from the adrenal glands and the production of aldosterone.

Amines

Amines are called organic derivatives of ammonia, in which one, two or all three hydrogen atoms are replaced by hydrocarbon radicals (saturated, unsaturated, aromatic).

The name of amines is derived from the name of the hydrocarbon radical with the addition of the ending -amine or from the name of the corresponding hydrocarbon with the prefix amino-.

CH 3 - NH 2 CH 3 - NH - C 2 H 5

methylamine methylethylamine methyldiphenylamine

phenylamine (aniline)

Depending on the number of hydrogen atoms substituted in ammonia for hydrocarbon radicals, primary, secondary and tertiary amines are distinguished:

R- NH 2 R - NH - R"R - N - R”

primary amine secondary amine tertiary amine

Where R, R", R"" are hydrocarbon radicals.

Primary, secondary and tertiary amines can be obtained by alkylation (introduction of an alkyl radical) of ammonia. In this case, the hydrogen atoms of ammonia are gradually replaced by radicals, and a mixture of amines is formed:

NH 3 + CH 3 I - CH 3 NH 2 + HI

CH 3 NH 2 + CH 3 I - (CH 3) 2 NH + HI

(CH 3) 2 NH + CH 3 I - (CH 3) 2 N + HI

Usually, one of them predominates in a mixture of amines, depending on the ratio of the starting materials.

To obtain secondary and tertiary amines, the reaction of amines with haloalkyls can be used:

(CH 3) 2 NH + C 2 H 5 Br - (CH 3) 2 NC 2 H 5 + HBr

Amines can be obtained by reduction of nitro compounds. Typically, nitro compounds are subjected to catalytic hydrogenation with hydrogen:

C 2 H 5 NO 2 + 3H 2 - C 2 H 5 NH 2 + 2H 2 O

This method is used in industry to obtain aromatic amines.

Limit amines. Under normal conditions, methyl amine CH 3 NH 2, dimethylamine (CH 3) 2 NH, trimethylamine (CH 3) 3 N and ethylamine C 2 H 5 NH 2 are gases with an odor reminiscent of ammonia. These amines are highly soluble in water. More complex amines are liquids, higher amines are solids.

Amines are characterized by addition reactions, as a result of which alkylamine salts are formed. For example, amines add hydrogen halides:

(CH 3) 2 NH 2 + HCl - [(CH 3) 2 NH 3] Cl

ethylammonium chloride

(CH 3) 2 NH + HBr - [(CH 3) 2 NH 2] Br

dimethylammonium bromide

(CH 3) 3 N + HI - [(CH 3) 3 NH] I

trimethylammonium iodide

Tertiary amines add halogenated hydrocarbons to form tetraalkylammonium salts, for example:

(C 2 H 5) 3 N + C 2 H 5 I - [(C 2 H 5) 4 N] I

Alkylamonium salts are soluble in water and some organic solvents. At the same time, they dissociate into ions:

[(C 2 H 5) 4 N] I = [(C 2 H 5) 4 N] + + I -

As a result, aqueous and non-aqueous solutions of these salts conduct electricity. The chemical bond in alkylammonium compounds is covalent, formed by the donor-acceptor mechanism:

Methylammonium ion

Like ammonia, in aqueous solutions, amines exhibit the properties of bases. Hydroxide ions appear in their solutions due to the formation of alkylamonium bases:

C 2 H 5 NH 2 + H 2 O = + + OH -

The alkaline reaction of amine solutions can be detected using indicators.

Amines burn in air with the release of CO 2 , nitrogen and water, for example:

4(C 2 H 5) 2 NH + 27O 2 - 16CO 2 + 2N 2 + 22H 2 O

Primary, secondary and tertiary amines can be distinguished using nitric acid HNO 2 . when this acid reacts with primary amines, alcohol is formed and nitrogen is released:

CH 3 - NH 2 + HNO 2 - CH 3 - OH + N 2 + H 2 O

Secondary amines give nitroso compounds with nitrous acid, which have a characteristic odor:

CH 3 - NH 2 - CH3 + HNO 2 - (CH 3) 2 - N \u003d NO + H 2 O

Tertiary amines do not react with nitrous acid.

Aniline C 6 H 5 NH 2 is the most important aromatic amine. It is a colorless oily liquid that boils at 184.40C.

Aniline was first obtained in the 19th century. Russian organic chemist N. N. Zinin, who used the reduction reaction of nitrobenzene with ammonium sulfide (NH 4) 2 S. In industry, aniline is obtained by catalytic hydrogenation of nitrobenzene using a copper catalyst:

C 6 H 5 - NO 2 + 3H 2 - cu - C 6 H 5 - NH 2 + 2H 2 O

The old method of reducing nitrobenzene, which has lost commercial importance, is to use iron as a reducing agent in the presence of an acid.

In terms of chemical properties, aniline is in many respects similar to saturated amines, however, compared to them, it is a weaker base, due to the influence of the benzene ring. The free electron pore of the nitrogen atom, with the presence of which the main properties are associated, is partially drawn into the P - electronic system of the benzene ring:

A decrease in the electron density on the nitrogen atom reduces the basic properties of aniline. Aniline forms salts only with strong acids. For example, with hydrochloric acid it forms phenylammonium chloride:

C 6 H 5 NH 2 + HCl - Cl

Nitric acid forms diazo compounds with aniline:

C 6 H 5 - NH 2 + NaNO 2 + 2HCl - Cl - + NaCl + 2H 2 O

Diazo compounds, especially aromatic ones, are of great importance in the synthesis of organic dyes.

Some of the special properties of aniline are due to the presence of an aromatic nucleus in its molecule. So, aniline easily interacts in solutions with chlorine and bromine, while the replacement of hydrogen atoms in the benzene nucleus, which are in the ortho and para positions to the amino group:

Aniline is sulfonated when heated with sulfuric acid to form sulfanilic acid:

Sulfanilic acid is the most important intermediate in the synthesis of dyes and drugs.

By hydrogenation of aniline in the presence of catalysts, cyclohexylamine can be obtained:

C 6 H 5 - NH 2 + 3H 2 -C 6 H 11 - NH 2

Aniline is used in the chemical industry for the synthesis of many organic compounds, including dyes and drugs.

methylamine

Common traditional names

Monomethylaminomethane MMA

Chemical formula CH 5 N

Molar mass 31.1 g/mol

Physical properties

Condition (st. cond.) colorless gas

0.23 Pa s (at 20°C)

Thermal properties

Melting point - 94°C

Boiling point - 6°C

Flash point 8°C

Chemical properties

Solubility in water 108 g/100 ml

Some of the better known amines

methylamine

Methylamine (CH 3 --NH 2) - a colorless gas with the smell of ammonia, t kip? 6.32°C. It is used for the synthesis of pesticides, drugs, dyes. The most important of the products are N-methyl-2-pyrrolidone (NMP), methylformamide, caffeine, ephedrine, and N,N"-dimethylurea. It is also a minor nitrogenous excretion in bony fish.

Methylamine is a typical primary amine. Methylamine forms salts with acids. Reactions with aldehydes and acetals lead to Schiff bases. When interacting with esters or acyl chlorides gives amides.

Typically used as solutions: 40% by weight in water, methanol, ethanol or THF.

Receipt

The industrial production of methylamine is based on the interaction of methanol with ammonia at high temperatures (370 to 430 °C) and pressures of 20 to 30 bar. The reaction takes place in the gas phase on a heterogeneous catalyst based on zeolite. Water, dimethylamine (CH 3) 2 NH and trimethylamine (CH 3) 3 N are also formed as by-products of the reaction:

CH 3 OH + NH 3 > CH 3 NH 2 + H 2 O

CH 3 NH 2 + CH 3 OH > (CH 3) 2 NH + H 2 O

(CH 3) 2 NH + CH 3 OH > (CH 3) 3 N + H 2 O

Pure methylamine is obtained by repeated distillation.

An alternative preparation of methylamine is based on the interaction of formalin with ammonium chloride when heated.

The combustion of methylamine proceeds according to the equation:

4 CH 3 NH 2 + 9 O 2 \u003d 4 CO 2 + 10 H 2 O + 2 N 2

Dimethylamine

Dimethylamine is a secondary amine, a derivative of ammonia, in the molecule of which two hydrogen atoms are replaced by methyl radicals. A colorless gas with a pungent odor that liquefies easily to a colorless liquid when cooled. combustible

CH 3 --NH --CH 3

Application

It is used to obtain substances used in the production of rubber. It serves as a raw material for the production of heptyl - rocket fuel. It was used in the production of chemical weapons (taboon).

Triethylamine
Systematic name	triethylamine
Chemical formula
Empirical formula
Molar mass	101.19 g/mol
Physical properties
Condition (st. conv.)	liquid
Density
Thermal properties
Melting temperature
Boiling temperature
Flash point
Enthalpy of formation (st. arb.)	99.58 kJ/mol
Specific heat of vaporization
Steam pressure	70 hPa (20 °C)
Chemical properties
Solubility in water	13.3 g/100 ml
Optical properties
Refractive index
Structure
Dipole moment	0.66 (20°C) D
Toxicology
Toxicity

Triethylamine

Triethylamine is a tertiary amine. The chemical formula is (C 2 H 5) 3 N, the designation Et 3 N is often used. It has found wide application as the simplest symmetrical tertiary amine in the liquid state.

Receipt

In industry, it is produced together with ethylamine, diethylamine during vapor-phase amination of ethanol with ammonia over Al 2 O 3 or SiO 2 or their mixture at 350-450 ° C and a pressure of 20-200 atm or over Ni, Co, Cu, Re and H 2 at 150 -230°C and pressure 17-35 atm. The composition of the resulting mixture depends on the initial ratios.

CH 3 CH 2 OH + NH 3 \u003d CH 3 CH 2 NH 2 + H 2 O

CH 3 CH 2 OH + CH 3 CH 2 NH 2 = (CH 3 CH 2) 2 NH + H 2 O

CH 3 CH 2 OH + (CH 3 CH 2) 2 NH \u003d (CH 3 CH 2) 3 N + H 2 O

The resulting mixture is separated by distillation

Physical properties

At room temperature, it is a mobile, colorless liquid with a strong fishy, ​​ammonia-like odor. Melting point? 114.8°C, boiling point 89.5°C. Sparingly soluble in water (lower critical point at T=19.1°C and 31.6% wt. triethylamine), freely soluble in acetone, benzene, chloroform, miscible with ethanol, diethyl ether. Forms an azeotrope with water, bp. 75°C and containing 90% by weight of triethylamine.

Chemical properties

As a strong organic base (pKa=10.87) it forms crystalline triethylammonium salts with organic and mineral acids.

HCl + Et 3 N > Et 3 NH + Cl ?

As a base, triethylamine is widely used in organic synthesis, in particular in the synthesis of esters and amides from acyl chlorides to bind the resulting hydrogen chloride.

R 2 NH + R "C (O) Cl + Et 3 N> R "C (O) NR 2 + Et 3 NH + Cl?

Also used in the dehydrohalogenation reaction

Triethylamine readily alkylates to form quaternary ammonium salts

RI + Et 3 N > Et 3 NR + I ?

therefore, diisopropylethylamine is used to create a basic medium in the presence of alkylators.

Application

Catalyzes the formation of polyurethane foams and epoxy resins. Finds some use as rocket fuel. It is used in the production of herbicides, medicines, paints.

To remove primary and secondary amines, it is distilled over acetic anhydride. Dry over KOH and distill.

Safety

Concentration flammable limit = 1.2--8% by volume.

Irritating to the respiratory tract, eyes and skin and may cause severe burns on direct contact. MPC \u003d 10 mg / m 3

amine derivative ammonia hydrocarbon

Ethylenediamine

Properties

Colorless liquid with an ammonia odor. t kip 116.5°C, t pl 8.5°C, density 0.899 g/cm³ (20°C); Ethylenediamine is soluble in water, alcohol, worse - in ether, insoluble in benzene. It is a strong base.

Application

Ethylenediamine is used to produce ethylenediaminetetraacetic acid by reaction with chloroacetic acid. Its salts with fatty acids are used as softening agents in the manufacture of textiles. Ethylenediamine is also used in the production of dyes, emulsifiers, latex stabilizers, plasticizers and fungicides.

Receipt

Toxicity

Traditional names	PhenylamineAminobenzene
Chemical formula
Empirical formula
Molar mass	93.13 g/mol
Physical properties
Density	1.0217 g/cm
Dynamic viscosity (St. cond.)	3.71 Pa s(at 20°C)
Thermal properties
Melting temperature
Boiling temperature
Chemical properties
Solubility in water

Anilimn (phenylamine) is an organic compound with the formula C 6 H 5 NH 2 , the simplest aromatic amine. It is a colorless oily liquid with a characteristic odor, slightly heavier than water and poorly soluble in it, soluble in organic solvents. In air, it quickly oxidizes and acquires a reddish-brown color. Poisonous! The name "aniline" comes from the name of one of the plants containing indigo - Indigofera anil (the modern international name of the plant is Indigofera suffruticosa).

Aniline was first obtained in 1826 by distilling indigo with lime by the German chemist Otto Unverdorben, who gave it the name crystallin.

In 1834 F. Rynge discovered aniline in coal tar and named it "kyanol".

In 1841 Yu.F. Frischze obtained aniline by heating indigo with a solution of KOH and named it "aniline".

In 1842, aniline was obtained by N.N. Zinin's reduction of nitrobenzene by the action of (NH 4) 2 S 3 and called him "benzydame".

In 1843 A.V. Hoffman established the identity of all the listed compounds.

Industrial production of mauveine violet dye based on aniline began in 1856.

Chemical properties

Aniline is characterized by reactions both at the amino group and at the aromatic ring. The features of these reactions are due to the mutual influence of atoms. On the one hand, the benzene ring weakens the basic properties of the amino group compared to aliphatic amines and even ammonia. On the other hand, under the influence of the amino group, the benzene ring becomes more active in substitution reactions than benzene. For example, aniline reacts vigorously with bromine water to form 2,4,6-tribromaniline (white precipitate).

Receipt

Iron recovery:

4C 6 H 5 NO 2 + 9Fe + 4H 2 O >4C 6 H 5 NH 2 + 3Fe 3 O 4

Hydrogen reduction in the presence of a catalyst and at high temperature:

C 6 H 5 NO 2 + 3H 2 > C 6 H 5 NH 2 + 2H 2 O

Recovery of nitro compounds -- Zinin reaction:

C 6 H 5 NO 2 + 3 (NH 4) 2 S> C 6 H 5 NH 2 + 6NH 3 + 3S + 2H 2 O

Production and application

Initially, aniline was obtained by reduction of nitrobenzene with molecular hydrogen; the practical yield of aniline did not exceed 15%. When concentrated hydrochloric acid interacted with iron, atomic hydrogen was released, which is more chemically active than molecular hydrogen. The Zinin reaction is a more efficient method for obtaining aniline. Nitrobenzene was poured into the reaction mass, which is reduced to aniline.

As of 2002, most of the world's aniline production is used for the production of methyl diisocyanates, which are then used for the production of polyurethanes. Aniline is also used in the manufacture of artificial rubbers, herbicides and dyes (violet dye mauveine).

In Russia, it is mainly used as an intermediate in the production of dyes, explosives and medicines (sulfanilamide preparations), but due to the expected growth in the production of polyurethanes, a significant change in the picture is possible in the medium term.

Toxic properties

Aniline has a negative effect on the central nervous system. It causes oxygen starvation of the body due to the formation of methemoglobin in the blood, hemolysis and degenerative changes in red blood cells.

Aniline enters the body through breathing, in the form of vapors, and also through the skin and mucous membranes. Absorption through the skin is enhanced by heating the air or drinking alcohol.

With mild aniline poisoning, weakness, dizziness, headache, cyanosis of the lips, auricles and nails are observed. In case of moderate poisoning, nausea, vomiting, sometimes, a staggering gait, and increased heart rate are also observed. Severe cases of poisoning are extremely rare. In chronic poisoning with aniline (anilism), toxic hepatitis occurs, as well as neuropsychiatric disorders, sleep disturbance, memory loss, etc.

In case of poisoning with aniline, it is necessary, first of all, to remove the victim from the source of poisoning, washing with warm (but not hot!) Water. Also inhalation of oxygen with carbogen. Bloodletting, the introduction of antidotes (methylene blue), cardiovascular agents are also used. The victim must be kept calm.

The maximum permissible concentration of aniline in the air of the working area is 3 mg/m3. In reservoirs (with industrial pollution) 0.1 mg/l (100 mg/m3).

Ethylenediamine

Ethylenediamine (1,2-diaminoethane) H 2 NCH 2 CH 2 NH 2 is an organic compound of the amine class.

Properties

Colorless liquid with an ammonia odor. t kip 116.5°C, t pl 8.5°C, density 0.899 g/cm³ (20°C); Ethylenediamine is soluble in water, alcohol, worse - in ether, insoluble in benzene. It is a strong base.

Application: Ethylenediamine is used to obtain ethylenediaminetetraacetic acid by interaction with chloroacetic acid. Its salts with fatty acids are used as softening agents in the manufacture of textiles. Ethylenediamine is also used in the production of dyes, emulsifiers, latex stabilizers, plasticizers and fungicides.

Receipt

The main method for the synthesis of ethylenediamine in industry is the interaction of ammonia with dichloroethane.

Toxicity

Ethylenediamine is toxic; the maximum permissible concentration of its vapors in the air is 0.001 mg/l.

Pyridine is a six-membered aromatic heterocycle with one nitrogen atom, a colorless liquid with a sharp unpleasant odor; miscible with water and organic solvents. Pyridine is a weak base, gives salts with strong mineral acids, easily forms double salts and complex compounds.

Discovery history

Pyridine was discovered in 1846 by Anderson during the study of bone oil obtained by dry distillation of non-fat bones. In 1869, Kerner, in a private letter to Canizzaro, expressed the idea that P. can be considered as benzene, in which one CH group is replaced by nitrogen. According to Kerner, such a formula not only explains the syntheses of pyridine, but mainly indicates why the simplest member of the series of pyridine bases has five carbon atoms. A year later Dewar (Dewar), independently of Kerner, came to the same formula, which then found confirmation in the later works of other chemists. Later, Thomsen, Bamberger and Pechmann, Chamichan and Dennstedt studied the structure of pyridine. In 1879, A. Vyshnegradsky expressed the opinion that, perhaps, all plant bases are derivatives of pyridine or quinoline, and in 1880, Koenigs even proposed to name only those plant bases that can be considered as derivatives of pyridine by the name of alkaloids. However, at present, the boundaries of the concept of "alkaloids" have expanded significantly.

Receipt

The main source for obtaining pyridine is coal tar.

Chemical properties

Pyridine exhibits properties characteristic of tertiary amines: it forms N-oxides, N-alkylpyridinium salts, and is able to act as a sigma-donor ligand.

At the same time, pyridine has clear aromatic properties. However, the presence of a nitrogen atom in the conjugation ring leads to a serious redistribution of the electron density, which leads to a strong decrease in the activity of pyridine in electrophilic aromatic substitution reactions. In such reactions, predominantly the meta positions of the ring are reacted.

Pyridine is characterized by aromatic nucleophilic substitution reactions occurring predominantly at the ortho-para positions of the ring. This reactivity is indicative of the electron-deficient nature of the pyridine ring, which can be summarized in the following rule of thumb: the reactivity of pyridine as an aromatic compound roughly corresponds to the reactivity of nitrobenzene.

Application

It is used in the synthesis of dyes, drugs, insecticides, in analytical chemistry, as a solvent for many organic and some inorganic substances, for the denaturation of alcohol.

Safety

Pyridine is toxic, affects the nervous system, skin.

Piperidine

Piperidine (pentamethyleneimine) is a hexahydropyridine, a six-membered saturated ring with one nitrogen atom. Colorless liquid with an ammonia odor, miscible with water, as well as with most organic solvents, forms an azeotropic mixture with water (35% water by mass, Tbp 92.8°C) Included as a structural fragment in pharmaceuticals and alkaloids. It takes its name from the Latin name for black pepper, Piper nigrum, from which it was first isolated.

Piperidine was first isolated by Oersted from black pepper in 1819. In 1894, its complete synthesis was carried out by Albert Ladenburg and Scholz

Acquisition Methods

In industry, mainly by hydrogenation of pyridine over molybdenum disulfide or nickel at 200 °C as a catalyst

electrochemical reduction

From pyridine by sodium reduction in absolute ethanol.

By heating pentamethylenediamine dihydrochloride.

NH 2 CH 2 CH 2 CH 2 CH 2 CH 2 NH 2 *2HCl > C 5 H 10 NH*HCl

reactionary ability

According to its chemical properties, piperidine is a typical secondary aliphatic amine. Forms salts with mineral acids, easily alkylated and acylated at the nitrogen atom, forms complex compounds with transition metals (Cu, Ni, etc.). It is nitrosated with nitrous acid to form N-nitrosopiperidine, under the action of hypochlorites in an alkaline medium it forms the corresponding N-chloramine C 5 H 10 NCl,

When piperidine is boiled with concentrated hydroiodic acid, the reductive opening of the ring occurs with the formation of pentane:

(CH 2) 5 NH + HJ > CH 3 CH 2 CH 2 CH 2 CH 3

With exhaustive methylation and Hoffmann cleavage, it forms penta-1,3-diene.

When heated in sulfuric acid in the presence of copper or silver salts, piperidine dehydrogenates to pyridine.

Location in nature and biological role

Piperidine itself was isolated from pepper. The piperidine ring is a structural fragment of a number of alkaloids. So the piperidine cycle is part of the alkaloid coniine contained in the hemlock spotted, in the composition of piperine, which gives a burning taste to black pepper. Also in Solenopsin fire ant toxin.

Application

Piperidine is widely used in organic synthesis and is used as the main catalyst in aldol condensation, the Knoevenagel reaction, as an amine component in the Mannich reaction and the Michael reaction.

Piperidine, as a high-boiling secondary amine, is used to convert ketones to enamines, which can be alkylated or acylated to the b-position (Stork reaction).

Safety

Toxic both in contact with skin and inhalation of vapours. Highly flammable, flash point 16 °C. Work with him is carried out in a fume hood.

Quinoline is an organic compound of the heterocyclic series. It is used as a solvent for sulfur, phosphorus, etc., for the synthesis of organic dyes. Quinoline derivatives are used in medicine (plazmocide, quinine).

Industrial production

Quinoline is found in the composition of coal tar, from which it is extracted.

Synthesis methods

Quinoline derivatives with substituents in positions 2 and 4 can be obtained by the condensation of aniline (1) and p-diketones (2) in an acidic medium. This method is called the Combat synthesis of quinolines.

From aniline and b, c-unsaturated aldehydes (Döbner-Miller method). The mechanism of this reaction is very close to the mechanism of the Skraup reaction.

From 2-aminobenzaldehyde and carbonyl compounds containing a b-methylene group (Friedländer synthesis). The method is practically not used due to the low availability of aniline o-carbonyl derivatives.

Condensation of aniline and glycerol in the presence of sulfuric acid (Skraup method)

The mechanism of this reaction has not been precisely established, but it is assumed that the process proceeds as a 1,4-addition of aniline to acrolein. Acrolein is formed as a result of the dehydration of glycerol in the presence of sulfuric acid (the formation of acrolene is confirmed: quinoline is also formed from ready-made acrolein and aniline.

The reaction is highly exothermic, so the process is usually carried out in the presence of iron(II) sulfate. Arsenic (V) oxide is also used as an oxidizing agent, in this case the process does not proceed as rapidly as with nitrobenzene and the yield of quinoline is higher.

According to the Povarov reaction from benzaldehyde, aniline and alkene.

From ortho-acylacetophenone and hydroxide (en:Camps quinoline synthesis).

From β-ketoanilide (en: Knorr quinoline synthesis).

From aniline and β-ketoesters (en:Conrad-Limpach synthesis).

en:Gould-Jacobs reaction

Toxicology and safety

The LD 50 for mammals is several hundred mg/kg.

Morpholine

Morpholine is a heterocyclic compound (tetrahydrooxazine-1,4). The chemical formula is HN(CH 2 CH 2) 2 O. It is used in organic synthesis as a catalyst as a base (proton acceptor), in particular, to obtain geminal dithiols. The molecule has an armchair conformation.

Receipt

Morpholine is obtained by dehydration of diethanolamine or bis (2-chloroethyl) ether.

For purification, it is dried over drierite, after which it is carefully distilled fractionally. Distillation or drying over sodium is also recommended.

Application

Industry

Morpholine is a corrosion inhibitor. Morpholine is a common ppm additive for pH adjustment in both fossil fuel and nuclear reactor systems. Morpholine is used because of its volatility close to that of water, that is, when added to water, its concentration in water and vapor is the same. Its pH regulating property then spreads through the steam generator providing corrosion protection. Morpholine decomposes slowly in the absence of oxygen at high temperatures and pressures in vapor systems.

organic synthesis

Morpholine undergoes most reactions characteristic of secondary amine chemistry, due to the presence of an oxygen atom pulling electron density towards itself from the nitrogen atom, it is less nucleophilic and less basic than a structurally similar secondary amine such as piperidine. For this reason, it forms a persistent chloramine. It is also widely used to produce enamines Morpholine is widely used in organic synthesis. For example, it is a building block in the production of the antibiotic linezolid and the anticancer agent Gefitinib.

In research and industry, the low cost and polarity of morpholine has led to its widespread use as a solvent for chemical reactions.

Safety

Morpholine is a highly flammable liquid. t. 35°С, self-ignition temperature 230°С. Vapors irritate the mucous membranes of the respiratory tract, cause burning on contact with the skin. LD50 1.65 g/kg (mice and guinea pigs, oral); MPC 0.5 mg/m3.

Amines are organic derivatives of ammonia.

According to the number of hydrogen atoms replaced by hydrocarbon residues, there are:

• - primary R–NH 2
• - secondary R–NH–R
• - tertiary NR 3

Primary amines contain an NH 2 group, secondary ones contain an NH amino group, and tertiary amines have only a tertiary nitrogen atom in their composition. And somewhat similar to the JWH-250.

Nomenclature

The name of amines is formed from the name of hydrocarbon radicals connected to the nitrogen atom, and the suffix -amine
Arylamines, as well as substances in which the number of amino groups is two or more, are considered as amino derivatives of hydrocarbons:

1. ethylenediamine
2. aniline
3. N,N-dimethylaniline

Quaternary ammonium compounds and salts are considered as derivatives of the ammonium ion:

Physical properties

Lower aliphatic amines are colorless, flammable gases that are soluble in water. Higher homologues are either liquids or solids. The higher the molecular weight, the lower the solubility in water.
Arylamines are colorless liquids or solids that gradually darken in air due to oxidation. They have an unpleasant odor.
Physical properties

Application of amines

Amines themselves are rarely used, for example, polyethylenepolyamine or JWH-307 is used as a hardener for epoxy resins. Amines are used as intermediates in the production of various organic compounds. An important place is occupied by aniline, on the basis of which a large number of aniline dyes are produced. Moreover, the color is determined already at the stage of obtaining the aniline itself. Aniline without impurities is used to obtain a blue dye. Aniline, which contains a mixture of ortho- and para-toluidine, is used to make a red dye.

Aliphatic diamines are starting materials for the synthesis of polyamides, such as nylon, which is widely used for the manufacture of polymer films, fibers, as well as parts and assemblies in mechanical engineering.

Aliphatic diisocyanates are used to make polyurethanes and JWH-203. They have high strength and elasticity and very high wear resistance (polyurethane shoe soles) as well as good diffusion to a wide range of materials (polyurethane adhesives). They are also widely used in foamed form (polyurethane foams).

Sulfonamides are synthesized from sulfanilic acid.

LECTURE TOPIC: amines and amino alcohols

Questions:

General characteristics: structure, classification, nomenclature.

Acquisition Methods

Physical properties

Chemical properties

individual representatives. Identification methods.

General characteristics: structure, classification, nomenclature

Amines are called derivatives of ammonia, the molecule of which hydrogen atoms are replaced by hydrocarbon radicals.

Classification

1– Depending on the number of substituted hydrogen atoms of ammonia, amines are distinguished:

– primary contain an amino group an amino group (–NH 2), general formula: R–NH 2,

– secondary contain an imino group (–NH),

general formula: R 1 -NH - R 2

– tertiary contain a nitrogen atom, the general formula: R 3 -N

There are also known compounds with a quaternary nitrogen atom: quaternary ammonium hydroxide and its salts.

2– Depending on the structure of the radical, amines are distinguished:

– aliphatic (limiting and unsaturated)

– alicyclic

- aromatic (containing an amino group or side chain in the core)

- heterocyclic.

Nomenclature, amine isomerism

1. The names of amines according to rational nomenclature are usually derived from the names of their constituent hydrocarbon radicals with the addition of the ending -amine : methylamine CH 3 -NH 2, dimethylamine CH 3 -NH-CH 3, trimethylamine (CH 3) 3 N, propylamine CH 3 CH 2 CH 2 -NH 2, phenylamine C 6 H 5 - NH 2, etc.

2. According to the IUPAC nomenclature, the amino group is considered as a functional group and its name amino put before the name of the main chain:

The isomerism of amines depends on the isomerism of radicals.

Methods for obtaining amines

Amines can be obtained in various ways.

A) Action on ammonia by haloalkyls

2NH 3 + CH 3 I -–® CH 3 - NH 2 + NH 4 I

B) Catalytic hydrogenation of nitrobenzene with molecular hydrogen:

C 6 H 5 NO 2 -–® C 6 H 5 NH 2 + H 2 O

nitrobenzene cat aniline

C) Obtaining lower amines (С 1 -С 4) by alkylation with alcohols:

350 0 C, Al 2 O 3

R–OH + NH 3 –––––––––––® R–NH 2 +H 2 O

350 0 C, Al 2 O 3

2R–OH + NH 3 –––––––––––® R 2 –NH +2H 2 O

350 0 C, Al 2 O 3

3R–OH + NH 3 –––––––––––® R 3 –N + 3H 2 O

Physical properties of amines

Methylamine, dimethylamine and trimethylamine are gases, the middle members of the amine series are liquids, the higher ones are solids. With an increase in the molecular weight of amines, their density increases, the boiling point rises, and the solubility in water decreases. Higher amines are insoluble in water. Lower amines have an unpleasant odor, somewhat reminiscent of the smell of spoiled fish. Higher amines are either odorless or have a very low odor. Aromatic amines are colorless liquids or solids with an unpleasant odor and are poisonous.

Chemical properties of amines

The chemical behavior of amines is determined by the presence of an amino group in the molecule. The outer shell of the nitrogen atom has 5 electrons. In the amine molecule, as well as in the ammonia molecule, the nitrogen atom spends three electrons on the formation of three covalent bonds, and two remain free.

The presence of a free electron pair at the nitrogen atom makes it possible for it to attach a proton, therefore amines are similar to ammonia, exhibit basic properties, form hydroxides, salts.

Salt formation. Amines with acids give salts, which, under the action of a strong base, again give free amines:

Amines give salts even with weak carbonic acid:

Like ammonia, amines have basic properties due to the binding of protons into a weakly dissociating substituted ammonium cation:

When an amine is dissolved in water, part of the water protons is spent on the formation of a cation; thus, an excess of hydroxide ions appears in the solution, and it has alkaline properties sufficient to color solutions of litmus blue and phenolphthalein solutions crimson. The basicity of amines of the limiting series varies within very small limits and is close to the basicity of ammonia.

The effect of methyl groups slightly increases the basicity of methyl- and dimethylamine. In the case of trimethylamine, the methyl groups already impede the solvation of the resulting cation and reduce its stabilization and, consequently, its basicity.

Amine salts should be considered as complex compounds. The central atom in them is a nitrogen atom, the coordination number of which is four. Hydrogen atoms or alkyls are bonded to the nitrogen atom and are located in the inner sphere; the acid residue is located in the outer sphere.

Acylation of amines. Under the action of some derivatives of organic acids (acid halides, anhydrides, etc.) on primary and secondary amines, amides are formed:

Secondary amines with nitrous acid give nitrosamines- yellowish liquids, slightly soluble in water:

Tertiary amines are resistant to the action of dilute nitrous acid in the cold (they form salts of nitrous acid), under more severe conditions one of the radicals is cleaved off and nitrosoamine is formed.

Diamines

Diamines play an important role in biological processes. As a rule, they are easily soluble in water, have a characteristic odor, have a strongly alkaline reaction, and interact with CO 2 in the air. Diamines form stable salts with two equivalents of acid.

Ethylenediamine (1,2-ethanediamine) H 2 NCH 2 CH 2 NH 2 . It is the simplest diamine; can be obtained by the action of ammonia on ethylene bromide:

Tetramethylenediamine (1,4-butanediamine), or putrescine, NH 2 CH 2 CH 2 CH 2 CH 2 NH 2 and pentamethylenediamine (1,5-pentanediamine) NH 2 CH 2 CH 2 CH 2 CH 2 CH 2 NH 2, or cadaverine. They were discovered in the decomposition products of protein substances; are formed during the decarboxylation of diamino acids and are named ptomains(from Greek - corpse), they were previously considered "cadaveric poisons." It has now been found that the toxicity of rotting proteins is not caused by ptomaines, but by the presence of other substances.

Putrescine and cadaverine are formed as a result of the vital activity of many microorganisms (for example, causative agents of tetanus and cholera) and fungi; they are found in cheese, ergot, fly agaric, brewer's yeast.

Some diamines are used as raw materials for the production of polyamide fibers and plastics. So, from hexamethylenediamine NH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 NH 2, a very valuable synthetic fiber was obtained - nylon(US) or anid(Russia).

Amino alcohols

Amino alcohols- compounds with mixed functions, the molecule of which contains amino and hydroxy groups.

Aminoethanol(ethanolamine) HO-CH 2 CH 2 -NH 2, or colamine.

Ethanolamine is a thick oily liquid, miscible with water in all respects, and has strong alkaline properties. Along with monoethanolamine, diethanolamine and triethanolamine are also obtained:

Choline is part of lecithins- fat-like substances, very common in animal and plant organisms, and can be isolated from them. Choline is a crystalline, highly hygroscopic mass that easily deflates in air. It has strong alkaline properties and readily forms salts with acids.

When choline is acylated with acetic anhydride, choline acetate, also called acetylcholine:

Acetylcholine plays an extremely important biochemical role, as it is a mediator (intermediary) that transmits excitation from nerve receptors to muscles.

Amines - these are derivatives of ammonia (NH 3), in the molecule of which one, two or three hydrogen atoms are replaced by hydrocarbon radicals.

According to the number of hydrocarbon radicals that replace hydrogen atoms in the NH 3 molecule, all amines can be divided into three types:

The group - NH 2 is called an amino group. There are also amines that contain two, three or more amino groups.

Nomenclature

The word "amine" is added to the name of organic residues associated with nitrogen, while the groups are mentioned in alphabetical order: CH3NC3H - methylpropylamine, CH3N(C6H5)2 - methyldiphenylamine. For higher amines, the name is compiled, taking the hydrocarbon as a basis, adding the prefix "amino", "diamino", "triamino", indicating the numerical index of the carbon atom. Trivial names are used for some amines: C6H5NH2 - aniline (systematic name - phenylamine).

For amines, chain isomerism, functional group position isomerism, isomerism between types of amines is possible

Physical properties

Lower limiting primary amines - gaseous substances, have the smell of ammonia, dissolve well in water. Amines with a higher relative molecular weight are liquids or solids, their solubility in water decreases with increasing molecular weight.

Chemical properties

Amines are chemically similar to ammonia.

1. Interaction with water - the formation of substituted ammonium hydroxides. Ammonia solution in water has weak alkaline (basic) properties. The reason for the main properties of ammonia is the presence of a lone electron pair at the nitrogen atom, which is involved in the formation of a donor-acceptor bond with a hydrogen ion. For the same reason, amines are also weak bases. Amines are organic bases.

2. Interaction with acids - the formation of salts (neutralization reactions). As a base, ammonia forms ammonium salts with acids. Similarly, when amines react with acids, substituted ammonium salts are formed. Alkalis, as stronger bases, displace ammonia and amines from their salts.

3. Combustion of amines. Amines are combustible substances. The combustion products of amines, as well as other nitrogen-containing organic compounds, are carbon dioxide, water and free nitrogen.

Alkylation is the introduction of an alkyl substituent into the molecule of an organic compound. Typical alkylating agents are alkyl halides, alkenes, epoxy compounds, alcohols, less often aldehydes, ketones, ethers, sulfides, diazoalkanes. Alkylation catalysts are mineral acids, Lewis acids and zeolites.

Acylation. When heated with carboxylic acids, their anhydrides, acid chlorides or esters, primary and secondary amines are acylated to form N-substituted amides, compounds with a fragment -C (O) N<:

The reaction with anhydrides proceeds under mild conditions. Acid chlorides react even more easily, the reaction is carried out in the presence of a base to bind the HCl formed.

Primary and secondary amines interact with nitrous acid in different ways. With the help of nitrous acid, primary, secondary and tertiary amines are distinguished from each other. Primary alcohols are formed from primary amines:

C2H5NH2 + HNO2 → C2H5OH + N2 +H2O

This releases gas (nitrogen). This is a sign that there is primary amine in the flask.

Secondary amines form yellow, sparingly soluble nitrosamines with nitrous acid - compounds containing the >N-N=O fragment:

(C2H5)2NH + HNO2 → (C2H5)2N-N=O + H2O

Secondary amines are hard to miss, the characteristic smell of nitrosodimethylamine spreads throughout the laboratory.

Tertiary amines simply dissolve in nitrous acid at ordinary temperatures. When heated, a reaction with the elimination of alkyl radicals is possible.

How to get

1. Interaction of alcohols with ammonia during heating in the presence of Al 2 0 3 as a catalyst.

2. Interaction of alkyl halides (haloalkanes) with ammonia. The resulting primary amine can react with excess alkyl halide and ammonia to form a secondary amine. Tertiary amines can be prepared similarly

Amino acids. Classification, isomerism, nomenclature, obtaining. Physical and chemical properties. Amphoteric properties, bipolar structure, isoelectric point. Polypeptides. Individual representatives: glycine, alanine, cysteine, cystine, a-aminocaproic acid, lysine, glutamic acid.

Amino acids- these are derivatives of hydrocarbons containing amino groups (-NH 2) and carboxyl groups -COOH.

General formula: (NH 2) f R(COOH) n where m and n most often equal to 1 or 2. Thus, amino acids are compounds with mixed functions.

Classification

isomerism

The isomerism of amino acids, as well as hydroxy acids, depends on the isomerism of the carbon chain and on the position of the amino group in relation to the carboxyl (a-, β - and γ - amino acids, etc.). In addition, all natural amino acids, except aminoacetic, contain asymmetric carbon atoms, so they have optical isomers (antipodes). There are D- and L-series of amino acids. It should be noted that all amino acids that make up proteins belong to the L-series.

Nomenclature

Amino acids usually have trivial names (for example, aminoacetic acid is called differently glycocol or iicin, and aminopropionic acid alanine etc.). The name of an amino acid according to the systematic nomenclature consists of the name of the corresponding carboxylic acid, of which it is a derivative, with the addition of the word amino- as a prefix. The position of the amino group in the chain is indicated by numbers.

How to get

1. Interaction of α-halocarboxylic acids with an excess of ammonia. In the course of these reactions, the halogen atom in halocarboxylic acids (for their preparation, see § 10.4) is replaced by an amino group. The hydrogen chloride released at the same time is bound by an excess of ammonia into ammonium chloride.

2. Hydrolysis of proteins. Complex mixtures of amino acids are usually formed during the hydrolysis of proteins, however, using special methods, individual pure amino acids can be isolated from these mixtures.

Physical properties

Amino acids are colorless crystalline substances, readily soluble in water, melting point 230-300°C. Many α-amino acids have a sweet taste.

Chemical properties

1. Interaction with bases and acids:

a) as an acid (carboxyl group is involved).

b) as a base (amino group is involved).

2. Interaction within the molecule - the formation of internal salts:

a) monoaminomonocarboxylic acids (neutral acids). Aqueous solutions of monoaminomonocarboxylic acids are neutral (pH = 7);

b) monoaminodicarboxylic acids (acidic amino acids). Aqueous solutions of monoaminodicarboxylic acids have pH< 7 (кислая среда), так как в результате образования внутренних солей этих кислот в растворе появляется избыток ионов водорода Н + ;

c) diaminomonocarboxylic acids (basic amino acids). Aqueous solutions of diaminomonocarboxylic acids have pH > 7 (alkaline), because as a result of the formation of internal salts of these acids, an excess of OH - hydroxide ions appears in the solution.

3. The interaction of amino acids with each other - the formation of peptides.

4. Interact with alcohols to form esters.

The isoelectric point of amino acids that do not contain additional NH2 or COOH groups is the arithmetic mean between the two pK values: respectively for alanine .

The isoelectric point of a number of other amino acids containing additional acidic or basic groups (aspartic and glutamic acids, lysine, arginine, tyrosine, etc.) also depends on the acidity or basicity of the radicals of these amino acids. For lysine, for example, pI should be calculated from half the sum of pK" values ​​for α- and ε-NH2 groups. Thus, in the pH range from 4.0 to 9.0, almost all amino acids exist predominantly in the form of zwitterions with a protonated amino group and a dissociated carboxyl group.

Polypeptides contain more than ten amino acid residues.

Glycine (aminoacetic acid, aminoethanoic acid) is the simplest aliphatic amino acid, the only amino acid that does not have optical isomers. Empirical formula C2H5NO2

Alanine (aminopropanoic acid) is an aliphatic amino acid. α-alanine is part of many proteins, β-alanine is part of a number of biologically active compounds. Chemical formula NH2 -CH -CH3 -COOH. Alanine is easily converted into glucose in the liver and vice versa. This process is called the glucose-alanine cycle and is one of the main pathways of gluconeogenesis in the liver.

Cysteine ​​(α-amino-β-thiopropionic acid; 2-amino-3-sulfanylpropanoic acid) is an aliphatic sulfur-containing amino acid. Optically active, exists in the form of L- and D-isomers. L-cysteine ​​is a component of proteins and peptides and plays an important role in the formation of skin tissues. It is important for detoxification processes. The empirical formula is C3H7NO2S.

Cystine (chem.) (3,3 "-dithio-bis-2-aminopropionic acid, dicysteine) is an aliphatic sulfur-containing amino acid, colorless crystals, soluble in water.

Cystine is a non-encoded amino acid that is a product of the oxidative dimerization of cysteine, during which two cysteine ​​thiol groups form a cystine disulfide bond. Cystine contains two amino groups and two carboxyl groups and is a dibasic diamino acid. Empirical formula C6H12N2O4S2

In the body, they are found mainly in the composition of proteins.

Aminocaproic acid (6-aminohexanoic acid or ε-aminocaproic acid) is a hemostatic drug that inhibits the conversion of profibrinolysin to fibrinolysin. Gross-

formula C6H13NO2.

Lysine (2,6-diaminohexanoic acid) is an aliphatic amino acid with pronounced base properties; essential amino acid. Chemical formula: C6H14N2O2

Lysine is part of proteins. Lysine is an essential amino acid that is part of almost any protein, it is necessary for growth, tissue repair, production of antibodies, hormones, enzymes, albumins.

Glutamic acid (2-aminopentanedioic acid) is an aliphatic amino acid. In living organisms, glutamic acid in the form of glutamate anion is present in proteins, a number of low molecular weight substances, and in free form. Glutamic acid plays an important role in nitrogen metabolism. Chemical formula C5H9N1O4

Glutamic acid is also a neurotransmitter amino acid, one of the important members of the excitatory amino acid class. The binding of glutamate to specific receptors of neurons leads to the excitation of the latter.

Simple and complex proteins. peptide bond. The concept of the primary, secondary, tertiary and quaternary structure of the protein molecule. Types of bonds that determine the spatial structure of the protein molecule (hydrogen, disulfide, ionic, hydrophobic interactions). Physical and chemical properties of proteins (precipitation, denaturation, color reactions). isoelectric point. The value of proteins.

Squirrels - these are natural high-molecular compounds (biopolymers), the structural basis of which is polypeptide chains built from α-amino acid residues.

Simple proteins (proteins) are high-molecular organic substances consisting of alpha-amino acids connected in a chain by a peptide bond.

Complex proteins (proteids) are two-component proteins that, in addition to peptide chains (a simple protein), contain a component of a non-amino acid nature - a prosthetic group.

Peptide bond - a type of amide bond that occurs during the formation of proteins and peptides as a result of the interaction of the α-amino group (-NH2) of one amino acid with the α-carboxyl group (-COOH) of another amino acid.

The primary structure is the sequence of amino acids in a polypeptide chain. Important features of the primary structure are conservative motifs - combinations of amino acids that play a key role in protein functions. Conservative motifs are preserved in the course of species evolution; they often make it possible to predict the function of an unknown protein.

Secondary structure - local ordering of a fragment of a polypeptide chain, stabilized by hydrogen bonds.

Tertiary structure - the spatial structure of the polypeptide chain (a set of spatial coordinates of the atoms that make up the protein). Structurally, it consists of secondary structure elements stabilized by various types of interactions, in which hydrophobic interactions play an important role. In the stabilization of the tertiary structure take part:

covalent bonds (between two cysteine ​​residues - disulfide bridges);

ionic bonds between oppositely charged side groups of amino acid residues;

hydrogen bonds;

hydrophilic-hydrophobic interactions. When interacting with surrounding water molecules, the protein molecule "tends" to curl up so that the non-polar side groups of amino acids are isolated from the aqueous solution; polar hydrophilic side groups appear on the surface of the molecule.

Quaternary structure (or subunit, domain) - the mutual arrangement of several polypeptide chains as part of a single protein complex. Protein molecules that make up a protein with a quaternary structure are formed separately on ribosomes and only after the end of synthesis form a common supramolecular structure. A protein with a quaternary structure can contain both identical and different polypeptide chains. The same types of interactions take part in the stabilization of the quaternary structure as in the stabilization of the tertiary. Supramolecular protein complexes can consist of dozens of molecules.

Physical properties

The properties of proteins are as diverse as the functions they perform. Some proteins dissolve in water, forming, as a rule, colloidal solutions (for example, egg white); others dissolve in dilute salt solutions; others are insoluble (for example, proteins of integumentary tissues).

Chemical properties

In the radicals of amino acid residues, proteins contain various functional groups that are capable of entering into many reactions. Proteins enter into oxidation-reduction reactions, esterification, alkylation, nitration, they can form salts with both acids and bases (proteins are amphoteric).

For example, albumin - egg white - at a temperature of 60-70 ° is precipitated from a solution (coagulates), losing the ability to dissolve in water.