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Complete reduction of adipic acid nitrile with hydrogen equation. Nitriles of carboxylic acids




1. Anhydrides of carboxylic acids

Anhydrides of carboxylic acids are products of the elimination of a water molecule from two acid molecules.

1.1. Methods for the preparation of carboxylic anhydrides

Anhydrides of carboxylic acids, as we have just seen (3.1), can be obtained from acid chlorides and salts of carboxylic acids. In addition, they can be obtained from acyl chlorides and carboxylic acids in the presence of pyridine:

acyl chloride acid pyridine anhydride pyridinium chloride

The anhydrides of many carboxylic acids are formed by heating the corresponding carboxylic acids, often with the use of dehydrating agents. So, acetic anhydride is obtained by heating acetic acid with concentrated sulfuric acid:

(28)

acetic anhydride

Cheap acetic anhydride is sometimes used as a dehydrating agent:

Exercise 19. Benzoic anhydride can be prepared by adding one mole equivalent of water to two mole equivalents of benzoyl chloride. Write this reaction.

Cyclic anhydrides of dicarboxylic acids are often formed by simply heating them:

(31)

succinic acid succinic anhydride

An industrial method for producing maleic anhydride is the oxidation of benzene or 2-butene with air:

(32)

Phthalic anhydride is produced industrially by the oxidation of naphthalene or o-xylene:

(33)

Acetic anhydride is produced industrially by the oxidation of acetaldehyde with atmospheric oxygen in the presence of a copper-cobalt catalyst:

Exercise 20. Maleic acid is converted to maleic anhydride at 200°C. To obtain maleic anhydride from fumaric acid, a much higher temperature is required. What explains this? Write the appropriate reactions.

Exercise 21. Write the reactions of propionic anhydride with (a) water, (b) ethanol, (c) ammonia, (d) ethylamine and describe their mechanism.

Exercise 22. What are the technical methods for obtaining acetic anhydride? What is its industrial application?

Exercise 23. Complete reactions

1.2. Reactions of anhydrides of carboxylic acids

Anhydrides of carboxylic acids enter into the same reactions as acid chlorides:

(35)

methyl acetate

(M 6)

(37)

acetamide

Compounds containing acetyl groups are most commonly prepared from acetic anhydride: it is cheap, readily available, not very volatile, and does not emit corrosive HCl.

(38)

acetic anhydride niline acetanilide

(M 7)

Exercise 24. Write the reactions of acetanhydride (a) with aniline and (b) salicylic acid and describe their mechanism.


Formally, ketenes can be considered as internal anhydrides of monocarboxylic acids RCH=C=O. The simplest ketene CH 2 \u003d C \u003d O is simply called ketene.

Ketene is obtained by high-temperature dehydration of acids

(39)

or pyrolysis of acetone

Ketene enters into addition reactions with the formation of the same products that can be obtained from acetic anhydride and acetyl chloride:

Ex. 25. Write the reactions of ketene with (a) water, (b) 1-propanol, (c) phenol, (d) methylamine, (e) aniline.

Ketene readily dimerizes to diketene:

Diketene enters into addition reactions according to the scheme:

acetoacetic ester

Ex. 26. Write the reactions of diketene with (a) water, (b) matanol, (c) ammonia, (d) aniline.


3. Nitriles

Nitriles are named in various ways:

CH 3 CN CH 2 \u003d CHCN PhCN NC (CH 2) 4 CN

ethanenitrile propenenitrile benzenecarbonitrile adiponitrile

(acetonitrile) (acrylonitrile) (benzonitrile)

3.1. Methods for obtaining nitriles

3.1.1. Obtaining nitriles by dehydration of amides

The dehydration of amides, which we discussed in the previous section, can serve as the last step in the chain of transformations of a carboxylic acid into a nitrile of this acid:

All these reactions are often combined in one process, passing a mixture of carboxylic acid and ammonia through alumina at 500 o C:

Exercise 46. Write the reaction of an industrial method for obtaining adiponitrile from adipic acid.

3.1.2. Obtaining nitriles by oxidative ammonolysis of hydrocarbons

When studying the oxidation of hydrocarbons, we saw that hydrocyanic acid (formic acid nitrile) and nitriles of other acids are obtained by oxidative ammonolysis of the corresponding hydrocarbons according to the scheme:

Exercise 47. Write the reactions for obtaining (a) acrylonitrile, (b) benzonitrile, (c) acetonitrile, and (d) terephthalic acid nitrile by oxidative monolysis of the corresponding hydrocarbons.

3.1.3. Obtaining nitriles by the Kolbe reaction

When halocarbons interact with potassium cyanide in aqueous ethanol, nitriles are formed by the S N 2 mechanism:

Since the cyanide anion is an ambident ion, isonitriles are formed as a by-product, which are removed by shaking the reaction mixture with dilute hydrochloric acid.

Exercise 48. Write the reactions for obtaining (a) propionitrile from ethylene, (b) butyronitrile from propylene, (c) succinic acid dinitrile from ethylene, (d) vinylacetic acid nitrile from propylene, (e) phenylacetic acid nitrile from toluene, (e) phenylacetic acid nitrile, ( f) adipic acid dinitrile from acetylene.

Exercise 49. Complete reactions:

(a)(b)

3.2. Reactions of nitriles

3.2.1. Hydrogenation of nitriles

Nitriles readily hydrogenate to amines. Hydrogenation is carried out either with hydrogen at the time of isolation (C 2 H 5 OH + Na) or catalytically:

Exercise 50. Write the hydrogenation reactions of (a) propionitrile, (b) butyronitrile, (c) succinic acid dinitrile, (d) vinylacetic acid nitrile, (e) phenylacetic acid nitrile, (f) adipic acid dinitrile.

3.2.2. Hydrolysis of nitriles

Nitriles obtained from alkyl halides and metal cyanides by the reaction of nucleophilic substitution are good starting products for the preparation of carboxylic acids. To do this, they are subjected to hydrolysis in the presence of acids or bases:

Exercise 51. What acids are formed during the hydrolysis of the following nitriles:

(a) propionitrile, (b) butyronitrile, (c) succinic acid dinitrile, (d) vinylacetic acid nitrile, (e) phenylacetic acid nitrile, (f) adipic acid dinitrile.

According to this scheme, phenylacetic acid is obtained from available benzyl chloride:

(87)

Exercise 52. Propose a scheme for the production of phenylacetic acid starting from toluene. Describe the mechanisms of the corresponding reactions.

Malonic acid is mainly obtained from chloroacetic acid according to the scheme:

Exercise 53. Proceeding from ethylene and other necessary reagents, propose a scheme for obtaining butanedioic (succinic) acid.

Exercise 54. Using the appropriate halocarbons and nitriles, suggest schemes for obtaining the following acids: (a) propionic acid from ethylene, (b) butyric acid from propylene, (c) succinic acid from ethylene, (d) vinylacetic acid from propylene, (e) phenylacetic acid from toluene, ( e) adipic acid from acetylene.

From the available cyanohydrins, a-hydroxy acids are obtained:

(89)

Exercise 55. Based on the appropriate aldehydes and ketones and other necessary reagents, propose schemes for the preparation of (a) 2-hydroxyoxypropionic acid and

(b) 2-methyl-2-hydroxypropionic acid.

3.3. Alcoholysis of nitriles

Nitriles react with hydrogen chloride to form imino chlorides:

(90)

iminochloride

The action of hydrogen chloride in alcohol on nitriles leads to the formation of imino ester hydrochlorides, further hydrolysis of which gives esters:

Methyl methacrylate is industrially obtained from acetone via cyanohydrin:

acetone acetone cyanohydrin methyl methacrylate

A polymer of methyl methacrylate - polymethyl methacrylate is used in the manufacture of safety glasses (plexiglass).

Ex. 56. What product is formed as a result of the successive action of potassium cyanide, ethanol in the presence of hydrogen chloride and, finally, water on benzyl chloride? Write the appropriate reactions.

Ex. 57. What product is formed as a result of the successive action of hydrocyanic acid on acetaldehyde, and then methanol in the presence of sulfuric acid? Write the appropriate reactions.


4. Cyanamide

Of great practical importance is hydrocyanic acid amide - cyanamide. In industry, it is obtained from calcium carbide and nitrogen at 1000-1100 about C or at 650-800 about C in the presence of about 10% calcium chloride.

calcium cyanamide

The resulting mixture of calcium cyanamide and carbon black is directly used as fertilizer. When sulfuric acid acts on calcium cyanamide, cyanamide is obtained:

In the solid state and in solutions, cyanamide is in equilibrium with carbodiimide:

cyanamide carbodiimide

Urea is obtained by partial hydrolysis of cyanamide:

(94)

Under the action of hydrogen sulfide on cyanamide, thiourea is formed:

(95)

thiourea

Its interaction with ammonia leads to the formation of guanidine:

(96)

guanidine

When heated, cyanamide turns into melamine.

Nitriles of acids are also called cyanides, since they can be considered as a combination of a hydrocarbon radical with a cyano group. Usually, the names of nitriles are derived from the names of the corresponding acids:

Properties. The simplest nitriles are liquids with a rather pleasant smell, having a boiling point somewhat lower than the corresponding acids. Slightly poisonous, in contrast to the extremely poisonous hydrocyanic acid which can be considered as formic acid nitrile. The simplest nitriles are poorly soluble in water.

Nitriles are neutral substances. Upon hydrolysis in the presence of acids or alkalis, acid amides (with one water molecule) or free carboxylic acids (with two water molecules) are formed:

When nitriles are reduced with hydrogen (at the time of isolation), primary amines are formed:

Ways to get. We have already mentioned the preparation of nitriles by the interaction of alkyl halides with hydrocyanic acid salts, as well as by removing a water molecule from acid amides (pp. 67 and 146). The first of these methods is important for the preparation of carboxylic acids from alkyl halides. In this case, carboxylic acids are obtained with a larger number of carbon atoms than in the original halide alkyl. So; for example, to obtain propionic acid, one should proceed from ethyl bromide:

Acrylonitrile Liquid with temp. bale 78 It is an important starting material for the production of synthetic rubbers, plastics and synthetic fibers, as well as for the synthesis of other derivatives of acrylic acid.

In industry, acrylonitrile is obtained by three main methods.

1. Obtaining from ethylene oxide and hydrocyanic acid:

2. Obtaining from acetylene and hydrocyanic acid:

To obtain acrylonitrile by this method, acetylene is first mixed with hydrogen cyanide (12:1) and the resulting mixture, heated to 80 ° C, is fed under slight pressure into the reactor, in which the catalyst is located - an acidified solution of copper chloride, sodium and potassium chlorides. From the resulting gas-vapor mixture, acrylonitrile is completely absorbed further by water in the absorption column. The yield of acrylonitrile a is about 85%, counting on the starting acetylene.,

3. Direct synthesis from propylene and ammonia:

The process is carried out in column-type apparatuses at 450 °C and a pressure of about 100 °C in the presence of water vapor. Air oxygen is used as an oxidizing agent. Excess ammonia in the gas-vapor mixture is neutralized with sulfuric acid. Acrylonitrile and reaction by-products are absorbed by water; the aqueous solution is rectified.

This method of obtaining acrylonitrile is the most cost-effective and promising, as a result of which the first two methods will not be developed in the future.


Nitrile is a synthetic rubber (rubber). It is characterized by excellent resistance to high temperatures, resistance to oils, oil and petroleum products, low concentration acids and alkalis, and high slip resistance.

Nitrile is produced by polymerization, a mixture of butadiene and acrylonitrile. The original elements are converted and the result is a nitrile elastomer. The main raw material for the production of nitrile is oil.

Nitrile butadiene rubber can be used in combination with natural, isoprene, butadiene and styrene butadiene rubbers, which are introduced to improve the technological properties of mixtures and increase the frost resistance of vulcanizates. Combining them with ethylene-propylene and chloroprene rubbers improves ozone resistance and resistance to thermal aging, and combining them with thiokols, polyvinyl chloride, fluororubbers and phenol-formaldehyde resins improves oil and gasoline resistance, ozone resistance.

Due to the high resistance to oils and other aggressive agents, nitrile butadiene rubbers are widely used for the manufacture of various oil and petrol resistant rubber technical products - gaskets, sleeves, rings, cuffs, oil seals, technical plates MBS, petrol tanks, etc.

Rubbers are used for the production of insulating and electrically conductive rubbers, heels and soles of shoes, adhesives and ebonites, protective coatings that are resistant to aggressive environments.

Shoe sole based on a combination of nitrile and polyurethane

The sole made on the basis of nitrile rubber, this material deserves special attention!

Advantages: possesses high physical-mechanical and antistatic properties, resistance to high temperatures (up to +300°С), elasticity at low (up to -40°С) temperatures.

Nitrile rubber is also resistant to aggressive environments (possesses acid-base balance and MBS properties).

Its disadvantages include: relatively large weight.

  • strength;
  • elasticity;
  • resistance to chemicals.
  • Ozone resistant.
  • Oil resistant.
  • Acid resistant.
  • Heat resistant.
  • Resistant to aggressive environment.

In some cases, the characteristics may differ from those given above. For example, if an entrepreneur is looking for work gloves for agricultural work, they do not need to have fireproof properties, therefore, they do not need to be nitrile coated. From this we can conclude that the final choice of work gloves depends on the unique characteristics of the enterprise. quality gloves ensure the safety of employees, so choose them wisely.

Properties

Necessary if you are a medical worker from the field of surgery, cosmetology, pharmacology, etc. They are used in any kind of medicine where sterility is needed - laboratory research, dentistry, blood sampling, etc.

nitriles
Nitriles- organic compounds of the general formula R-C≡N, which are formally C-substituted hydrocyanic acid derivatives HC≡N.
  • 1 Nomenclature
  • 2 Structure of the nitrile group
  • 3 Physical and chemical properties
  • 4 Getting
  • 5 Impact on the human body
  • 6 Application
  • 7 Notes
  • 8 Literature
  • 9 See also

Nomenclature

Nitriles are also often considered as derivatives of carboxylic acids (amide dehydration products) and are referred to as derivatives of the corresponding carboxylic acids, for example, CH3C≡N - acetonitrile (acetic acid nitrile), C6H5CN - benzonitrile (benzoic acid nitrile). The systematic nomenclature for naming nitriles uses the suffix carbonitrile, for example, pyrrole-3-carbonitrile.

Nitriles in which the -C≡N group is mobile or has a pseudohalogen character are usually called cyanides, for example, C6H5CH2CN - benzyl cyanide, C6H5COCN - benzoyl cyanide, (CH3) 3SiCN - trimethylsilyl cyanide.

The structure of the nitrile group

The nitrogen and carbon atoms in the nitrile group are in a state of sp hybridization. The length of the triple bond C≡N is 0.116 nm, the length of the R-CN bond is 0.1468 nm (for CH3CN). The nitrile group has negative mesomeric and inductive effects, in particular, the Hammett constant σM = 0.56; σn = 0.66; σn- = 1.00; σn+ = 0.659, and Taft's inductive constant σ* = 3.6.

The electronic structure of nitriles can be represented as two resonant structures:

In the IR and Raman spectra, the nitrile group has an absorption band in the region of 222-2270 cm-1.

Physical and chemical properties

Nitriles are liquid or solid substances. They dissolve in organic solvents. Lower nitriles are highly soluble in water, but as their molar mass increases, their solubility in water decreases.

Nitriles are capable of reacting both with electrophilic reagents at the nitrogen atom and with nucleophilic reagents at the carbon atom, which is due to the resonance structure of the nitrile group. The unshared electron pair on the nitrogen atom promotes the formation of complexes of nitriles with metal salts, for example, with CuCl, NiCl2, SbCl5. The presence of the nitrile group leads to a decrease in the dissociation energy of the C-H bond at the α-carbon atom. The C≡N bond is capable of attaching other atoms and groups.

Hydrolysis of nitriles in an acidic medium leads first to amides, then to the corresponding carboxylic acids:

Hydrolysis of nitriles in an alkaline medium gives salts of carboxylic acids.

The reaction of nitriles with hydrogen peroxide (Radzishevsky reaction) leads to amides:

The interaction of nitriles with alcohols in the presence of acid catalysts (Pinner reaction) makes it possible to obtain imidoester hydrohalides, which are further hydrolyzed to esters. Interaction with thiols in a similar reaction leads, respectively, to salts of thioimidates and esters of thiocarboxylic acids:

Under the action of hydrogen sulfide on nitriles, thioamides RC(S)NH2 are formed, under the action of ammonia, primary and secondary amines - amidines RC(NHR")=NH, under the action of hydroxylamine - amidoximes RC(NH2)=NOH, under the action of hydrazone - amidohydrazones RC( NH2)=NNH2.

The reaction of nitriles with Grignard reagents gives N-magnesium substituted ketimines, which are hydrolyzed to ketones in an acidic environment:

Nitriles react with unsaturated compounds (Ritter reaction) to form substituted amides:

Diels-Alder reacts with dienes:

The reduction of nitriles proceeds step by step until the formation of primary amines. Most often, the reaction is carried out with hydrogen on platinum, palladium (at 1-3 atm. 20-50 ° C) or nickel, cobalt catalysts (100-250 atm., 100-200 ° C) in the presence of ammonia. Under laboratory conditions, nitriles are reduced with sodium in ethanol, potassium aluminum hydride and sodium borohydride:

The reaction of nitriles with carbonyl compounds according to Knoevenagel leads to cyanoalkenes:

Receipt

Nitriles are obtained in the following ways:

Dehydration of amides, aldoximes, ammonium salts of carboxylic acids Alkylation of hydrocyanic acid salts By the Sandmeyer reaction Addition of hydrocyanic acid (used in industry) Co-oxidation of ammonia and hydrocarbons (oxidative ammonolysis)

The reaction proceeds at 400-500 °C, bismuth molybdates and phosphomolybdates, cerium molybdates and tungstates, etc. serve as catalysts:

Amine oxidation

Impact on the human body

Nitriles are poisonous to humans due to a violation of the action of cytochrome oxidase and inhibition of the function of oxygen transfer from the blood to the cells. The toxic effect is manifested both by inhalation of nitrile vapors and by ingestion through the skin or gastrointestinal tract.

Antidotes are amyl nitrite, sodium thiosulfate and glucose.

Application

Nitriles are used as solvents, radical chain polymerization initiators, raw materials for the production of monomers, medicines, pesticides, and plasticizers. They are widely used in the Ritter reaction as a nucleophilic reagent.

The most important are acetonitrile (solvent, adsorbent in the separation of butadiene from a mixture with butenes), acrylonitrile (monomer for producing synthetic fiber), adipodinitrile (raw material for the synthesis of adipic acid, caprolactam, hexamethylenediamine), benzonitrile.

Notes

Wiktionary has an article "nitrile"
  1. nitriles // IUPAC Gold Book
  2. carbonitriles // IUPAC Gold Book

Literature

  • Chemical Encyclopedia / Ed.: Knunyants I.L. and others. - M.: Soviet Encyclopedia, 1992. - T. 3 (Med-Pol). - 639 p. - ISBN 5-82270-039-8.
  • O. Ya. Neiland. Organic chemistry. - M.: Higher school, 1990. - 751 p. - 35,000 copies. - ISBN 5-06-001471-1.
  • Zilberman E.N. Nitrile reactions. M.: "Chemistry", 1972. - 448 p.

see also

  • Aminonitriles
  • Isonitriles
  1. Zilberman E.N. Nitrile reactions. - Moscow: Chemistry, 1972. - 448 p.