Adipic acid (1,4-butanedicarboxylic acid) HOOC(CH2)4COOH, molecular weight 146.14; colorless crystals; m.p. 153°C, b.p. 265°C/100 mmHg Art.; easily sublimes; d418=1.344; decomposition point 210-240°C; () = 4.54 (160°С), 2.64 (193°С); ; , , . Solubility in water (g per 100 g): 1.44 (15°C), 5.12 (40°C), 34.1 (70°C). Solubility in ethanol, in ether - limited.

Adipic acid has all the chemical properties characteristic of carboxylic acids. Forms salts, most of which are soluble in water. Easily esterified to mono- and diesters. Forms polyesters with glycols. Salts and esters of adipic acid are called adipinates. When interacting with NH3 and amines, adipic acid gives ammonium salts, which, upon dehydration, turn into adipamides. With diamines, adipic acid forms polyamides, with NH3 in the presence of a catalyst at 300–400 °C, adipodinitrile.

When adipic acid is heated with acetic anhydride, a linear polyanhydride HO[-CO(CH2)4COO-]nH is formed, upon distillation of which at 210°C an unstable cyclic anhydride (formula I) is obtained, which at 100°C again turns into a polymer. Above 225 °C, adipic acid cyclizes to cyclopentanone (II), which is more easily obtained by pyrolysis of calcium adipate.

In industry, adipic acid is obtained mainly by a two-stage oxidation of cyclohexane. At the first stage (liquid-phase oxidation with air at 142-145°C and 0.7 MPa), a mixture of cyclohexanone and cyclohexanol is obtained, separated by distillation. Cyclohexanone is used to produce caprolactam. Cyclohexanol is oxidized with 40-60% HNO3 at 55°C (NH4VO3 catalyst); the yield of adipic acid is 95%.

Adipic acid can also be obtained:

a) oxidation of cyclohexane with 50-70% HNO3 at 100-200°C and 0.2-1.96 MPa or N2O4 at 50°C;

b) oxidation of cyclohexene with ozone or HNO3;

c) from THF according to the scheme:

d) carbonylation of THF to adipic anhydride, from which the acid is obtained by the action of H2O.

Polymers and their conformations
Polymer molecules are an extensive class of compounds, the main distinguishing characteristics of which are high molecular weight and high conformational chain flexibility.

Life and work of Academician Grigory Alekseevich Razuvaev
This abstract contains information about the biography and research activities in the field of organic and organometallic chemistry of the outstanding Soviet chemist, Hero of the Social...

Federal Agency for Education

State educational institution higher professional education

Samara State Technical University

Department: « Organic chemistry»

“SYNTHESIS OF ADIPIC ACID”

Course work

Completed:

Supervisor:

Samara, 2007

1. Introduction

1.1. Properties of adipic acid

1.2. The use of adipic acid

1.3. Synthesis of adipic acid

2. Literary review. Methods for obtaining dicarboxylic and polycarboxylic acids

2.2. Condensation reactions

2.3. Michael reactions

2.4. Oxidative Methods

3. Experimental technique

Bibliography

1. Introduction

1.1. Properties adipic acid

Adipic acid (1,4-butanedicarboxylic acid) HOOC(CH 2) 4 COOH, molecular weight 146.14; colorless crystals; m.p. 153°C, b.p. 265°C/100 mmHg Art.; easily sublimes; d 4 18 = 1.344; decomposition point 210-240°C; () = 4.54 (160°С), 2.64 (193°С); ; , , . Solubility in water (g per 100 g): 1.44 (15°C), 5.12 (40°C), 34.1 (70°C). Solubility in ethanol, in ether - limited.

Adipic acid has all the chemical properties characteristic of carboxylic acids. Forms salts, most of which are soluble in water. Easily esterified to mono- and diesters. Forms polyesters with glycols. Salts and esters of adipic acid are called adipinates. When interacting with NH 3 and amines, adipic acid gives ammonium salts, which, upon dehydration, turn into adipamides. With diamines, adipic acid forms polyamides, with NH 3 in the presence of a catalyst at 300-400 ° C - adipodinitrile.

When adipic acid is heated with acetic anhydride, a linear polyanhydride is formed BUT [-CO (CH 2) 4 COO-] n H, during the distillation of which at 210°C an unstable cyclic anhydride (formula I) is obtained, which at 100°C again turns into a polymer. Above 225 °C, adipic acid cyclizes to cyclopentanone (II), which is more easily obtained by pyrolysis of calcium adipate.

In industry, adipic acid is obtained mainly by a two-stage oxidation of cyclohexane. At the first stage (liquid-phase oxidation with air at 142-145°C and 0.7 MPa), a mixture of cyclohexanone and cyclohexanol is obtained, separated by distillation. Cyclohexanone is used to produce caprolactam. Cyclohexanol is oxidized with 40-60% HNO 3 at 55°C (NH 4 VO 3 catalyst); the yield of adipic acid is 95%.

Adipic acid can also be obtained:

a) oxidation of cyclohexane with 50-70% HNO 3 at 100-200°C and 0.2-1.96 MPa or N 2 O 4 at 50°C;

b) oxidation of cyclohexene with ozone or HNO 3 ;

c) from THF according to the scheme:

d) carbonylation of THF to adipic anhydride, from which the acid is obtained by the action of H 2 O.

1.2. Application adipic acid

The main area of ​​application of adipic acid is the production of polyamide resins and polyamide fibers, and these markets have long been formed and are experiencing fierce competition from polyester and polypropylene.

The use of adipic acid in the production of polyurethanes is increasing. Now the growth rate of production and consumption of polyurethanes exceeds the growth rate of production and consumption of polyamides, especially polyamide fibers. For example, the demand for adipic acid from Western European polyurethane producers is constantly increasing, and today its growth rate is approximately 12-15% per year. However, the demand for polyamide (nylon) for plastics production is also increasing, especially in Asian region. This is explained by the fact that for the production of polyurethanes in the Asia-Pacific countries, polyethers are more often used, in the synthesis of which adipic acid does not take part, therefore up to 85% of adipic acid is used here in the production of polyamides. This feature has a ripple effect on the demand for adipic acid in the region, so the average annual growth rate of global demand for this product is projected at 3-3.5%. In Russia own production adipic acid is not yet available, although there are very favorable conditions for this: a developed raw material base (cyclohexanol, cyclohexanone, nitric acid), there are large consumers of end products (plasticizers, monomers). The prospective need for adipic acid for Russia is estimated at several tens of thousands of tons per year. AT Russian Federation adipic acid is used for the production of plasticizers, polyamides, pharmaceuticals, polyurethanes.

So, adipic acid is a strategically and economically important raw material in the production of polyhexamethylene adipamide (~ 90% of the acid produced), its esters, polyurethanes; food supplement(gives a sour taste, in particular in the production of soft drinks). That is, products based on adipic acid are wide application in the production of polyamides, plasticizers, polyesters, polyester resins for PU, PPU, in the industrial processing of glass, in the radio-electronic and electrical industry, in the production of disinfectants, in the food and chemical-pharmaceutical industries, in the production of varnishes and enamels, solvents, self-curing compositions.

1.3. Synthesis adipic acid

Into a 5 liter round bottom flask equipped with a mechanical stirrer, thermometer and separating funnel ca. In 1 liter, place 2100 g (16.6 mol) of 50% nitric acid ( specific gravity 1.32; in fume hood). The acid is heated almost to boiling and 1 g of ammonium vanadate is added. Start the stirrer and slowly add 500 g (5 mol) of cyclohexanol through a separating funnel. First, 40-50 drops of cyclohexanol are added and the reaction mixture is stirred until the reaction starts (4-5 min), which becomes noticeable by the evolution of nitrogen oxides (Note 3). Then the reaction flask is placed in an ice bath, the contents of the flask are cooled until the temperature of the mixture reaches 55-60 0 C. After that, cyclohexanol is added as soon as possible, maintaining the temperature within the limits indicated above. Toward the end of the oxidation (after 475 g of cyclohexanol had been added), the ice bath was removed; sometimes the flask even has to be heated in order to maintain the required temperature and to avoid cyclization of the adipic acid.

Stirring is continued for another hour after the addition of the entire amount of cyclohexanol. The mixture is then cooled to 0, the adipic acid is suction filtered, washed with 500 ml ice water and air dry overnight. The output of white crystals with so pl. 146-149 0 is 395-410g. By evaporation of the mother liquors, another 30-40 g of product with m.p. 141-144 0 С (note 4). Total yield of crude adipic acid: 415-440g, or 58-60% theoretical. (note 6). The resulting product is reasonably pure for most purposes; however, a purer product can be obtained by recrystallization of crude adipic acid from 700 ml of concentrated nitric acid sp. weight 1.42. cleaning losses are about 5%. Recrystallized adipic acid melts at 151-152 0 (Notes 6 and 7).

Notes.

1. It is suggested not to use a catalyst if the temperature of the reaction mixture, after the start of the reaction, is maintained at 85-90 0 (Hartman, private communication).

2. Used technical cyclohexanol, practically free of phenol. More than 90% of the product boiled within 158-163 0 .

3. It is very important that the oxidation begin before a significant amount of cyclohexanol is added, otherwise the reaction may become violent. The reaction must be carried out in a well-functioning fume hood.

4. Nitric acid mother liquors contain significant amounts of adipic acid mixed with glutaric and succinic acids. It turned out that the separation of these acids by crystallization is practically impractical. However, if nitric acid is removed by evaporation, and the remaining mixture of acids is esterified with ethyl alcohol, then a mixture of ethyl esters of succinic (bp. 121-126 0 /20mm), glutaric (bp. 133-138 0 /20mm) and adipic b.p. (142-147 0 /20mm) acids. These esters can be successfully separated by distillation.

5. The following modified recipe may give a better outcome. In a 3-liter flask equipped with a stirrer, reflux condenser and addition funnel, fixed in asbestos stoppers impregnated with liquid glass, place 1900 ml of 50% nitric acid (1262 ml of nitric acid sp. weight 1.42, diluted to 1900 ml) and 1 g of ammonium vanadate. The flask is placed in a water bath heated to 50-60 0 , and very slowly, with the stirrer running, 357 g (3.5 mol.) of technical cyclohexanol are added so that the bath temperature is maintained at 50-60 0 . This operation lasts 6-8 hours. The reaction is terminated by heating the water bath to boiling until the evolution of nitrogen oxides ceases (about 1 hour). The hot reaction mixture is siphoned off and allowed to cool. Yield of crude adipic acid: 372g (72% theoretical).

Asbestos plugs impregnated with liquid glass are prepared from a thin asbestos sheet cut into strips 2.5 cm wide. The strips are moistened with a solution of liquid glass and then wound, for example, on the front of a refrigerator until a cork is obtained. right size. After assembling the device, the corks are covered with liquid glass and left to harden overnight.

6. Nitric acid mother liquors after crystallization can replace part of the fresh acid in subsequent oxidation operations.

7. Adipic acid can also be recrystallized from 2.5 times (by weight) water or 50% alcohol. However, these solvents give less satisfactory results than nitric acid.

Other methods of obtaining.

Adipic acid can also be obtained by the oxidation of cyclohexane and cyclohexanone with nitric acid or potassium permanganate. The described method is based on the patents of DeutscheHydrierwerkeA.-G.

Other methods of preparation consist in the oxidation of cyclohexene with potassium dichromate and sulfuric acid and in the interaction of γ-bromobutyric ester with sodium malonic ester, followed by saponification and decarboxylation of the resulting triethyl ester of 1,4,4-butanetricarboxylic acid.

2. Literature review. Methods for obtaining dicarboxylic and polycarboxylic acids

2.1. Carboxylation and alkoxycarbonylation

The carboxyl group can be introduced in two ways. The first way is to use carbon monoxide in the presence of a catalyst, most often an organometallic compound. The second route uses the reaction of the carbanion with carbon dioxide. We will consider both of these methods separately.

(1) Carboxylation with carbon monoxide

This important method a review is devoted to the preparation of dicarboxylic acids. A typical example is the synthesis of maleic anhydrides by the reaction of acetylene with iron carbonyl in aqueous alkali (scheme (1)). The reaction product (1) when oxidized with potassium ferricyanide or nitric acid gives maleic anhydride. Alkoxycarbonylation of organic halides (RHal) with nickel carbonyl and alkali metal alkoxide was developed by Corey et al. and is used for the synthesis of dicarboxylic acid esters (Scheme (2)).

Mononitriles are obtained by modification of this method (scheme (3)). Apparently, there are no restrictions on the use of this reaction for the synthesis of dinitriles, although no such examples are presented in the original work. Maleimides can be obtained in high yield from the reaction of diphenylacetylene, carbon monoxide, and an aromatic nitro compound using hexadecacarbonylhexarodium (Rh 6 (CO)i 6 ) as a catalyst and a tertiary amine (pyridine, N-methylpyrrolidine) as a solvent (Scheme (4)). Carbon monoxide appears to act in these reactions as a reducing agent and as a carbonylating agent; the reaction mechanism is complex.

Aliphatic α,β- and β,γ-unsaturated acid amides are reacted with carbon monoxide in the presence of a suitable cobalt catalyst to form succinic or glutaric acid imides. Co 2 (CO) 8 is the best catalyst here, although both Raney cobalt and cobalt(II) acetate also catalyze this reaction. N-Substituted Acrylamides. the corresponding succinimides are obtained in high yield (scheme (5)). Similarly, other acrylamide derivatives can be used.

(2) Carboxylation with carbon dioxide

The transformation of organometallic compounds into salts of carboxylic acids upon interaction with carbon dioxide is a well-known reaction, which (scheme (6)) can be used to carry out both mono- and dicarboxylation. The formation of the dicarboxylic acid depends on the direction of the reaction of the initially formed sodium salt of phenylacetic acid with a local excess of benzyl sodium, which leads to the disodium derivative of phenylacetic acid.

A review is devoted to the preparation of sodium and potassium compounds, which also describes the details of typical experimental techniques. These organometallic compounds can be prepared either by direct reaction of available organic compounds (usually a halide) with an alkali metal, or by a transmetalation reaction, which is basically an acid-base reaction, both methods are shown using the preparation of phenylsodium as an example (schemes (7) and (8)).

Metallation reactions involving organolithium compounds are also discussed in the review. To obtain dicarboxylic acids, it is necessary to use organobismetallic compounds or organometallic reagents that already contain a carboxyl group. Despite the possibility of side reactions, these transformations are applicable to a variety of compounds. Next, we will look at the most important examples this reaction.

When treated with Grignard reagents, some allenecarboxylic acids can be converted to organometallic compounds. The subsequent reaction of these compounds with carbon dioxide (scheme (9)) leads to (1-alkylvinyl)malonic acids in good yield.

Alkylmalonic acids are obtained in good yield (scheme (10)) by reacting an aluminum-lithium derivative of a carboxylic acid (2) with carbon dioxide; in turn, the organometallic derivative (2) used in this reaction is obtained by hydroalumination of alkynes-1. For example, when interacting with 2 mol of diisobutylaluminum hydride, hexine-1 leads (in 85% yield) to the organometallic derivative (3) (scheme (11)), which, after treatment with methyllithium, gives (4). This compound reacts with carbon dioxide to form malonic acid, and, as shown in scheme (10), the reaction proceeds through the formation of intermediate (2).

Similarly, it is possible to carry out the conversion of acetylenes to malonic acids using gem-organoboron compounds of type (5) (scheme (12)); when using 2 mol of butyl lithium, a yield of 65-70% can be achieved. Another good method synthesis of derivatives of substituted malonic acid reaction of α-anions of esters with carbon dioxide. Anions are generated using diisopropylamidalithium in tetrahydrofuran,

and the further procedure is reduced to passing carbon dioxide into the anion solution. Subsequent processing leads to an almost pure product (scheme (13)). Excellent results have been obtained with hindered esters such as ethyl 2-methyl propionate; in this case no adverse reactions were observed. good example this reaction is the synthesis of adamantane-2,2-dicarboxylic acid. The method can also be used in the homocuban series; ester (6) can be converted to the corresponding malonic acid derivative (scheme (14)) without degradation or rearrangement of the "cellular" framework.

Using the path shown in scheme (15), a set of dicarboxylic acids can be obtained from butadiene. Under the action of sodium under strictly defined conditions, butadiene dimerizes with the formation of disodium octadiene. The resulting delocalized dianion reacts with carbon dioxide to give a mixture of three possible regioisomeric diene dicarboxylic acids, the hydrogenation of which results in sebacic, 2-ethyl-probic, and 2,5-diethyladipic acids in a ratio of 3.5:5:1, respectively. This important reaction, extended to aromatic compounds such as styrene and 2-methylstyrene, leads to adipic acid derivatives (Scheme (16)), both products being hydrogenated to the corresponding dicyclohexyl derivatives.

The dianion of cyclooctatetraene reacts with carbon dioxide to form a dicarboxylic acid, but the structure (7) previously proposed for this product is incorrect. Alternative formula (8) is consistent with the results on the electrocyclic ring opening of the precursor having trance- stereochemistry, in accordance with the Woodward-Hoffmann rule on the conservation of orbital symmetry (scheme (17)).

An effective reagent for introducing a carboxyl or alkoxycarbonyl group into various carbanions is methylmethoxymagnesium carbonate (MMC) (9). Usually, ketones are converted to esters of a-keto acids, however, the use of an excess of MMA can lead to the inclusion of two methoxycarbonyl groups, as, for example, in the preparation of a synthetically important diester (10) (Scheme (18)).

2.2. Condensation reactions

Most of the general approaches to the synthesis of di- and polycarboxylic acids use condensation reactions. These reactions include Claisen ester condensation and various reactions of malonic and oxalic acid derivatives.

Long chain dicarboxylic acid derivatives are prepared from available dicarboxylic acid derivatives by Claisen ester condensation. One can use, for example, N,N-dimethylsebacamate (11) (Scheme (19)), since only the ester and the adjacent α-methylene group are involved in the condensation.

Alkylation of anions obtained from esters of malonic acid or ethyl cyanoacetate is widely used for the synthesis of monocarboxylic acids, and, as can be seen from scheme (20), can also be used to obtain dicarboxylic acids. When using the corresponding esters of halogen acids as alkylating agents (Scheme (20)) this method can, in principle, make it possible to obtain various di- and polycarboxylic acids.

Another use of diethyl malonate is more specific, since the reaction of diethyl sodium malonate with appropriately protected ethyl glycidates leads to α,β-diethoxycarbonylbutyrolactones, which, upon subsequent hydrolysis, are converted to paraconic acids (12) (scheme (21)). Treatment of paraconic acids with polyphosphoric acid gives the corresponding cyclolenten-2-ones-1, including dihydrojasmone,

Dehydrobenzenes react with malonic esters to give derivatives of homophthalic acid. For example, the reaction of diethyl malonate with about-bromoanisole in tetrahydrofuran in the presence of sodium amide gives 3-methoxyhomophthalimide in 60% yield; when the reaction conditions change, other products may appear. When using bromobenzene as a source of dehydrobenzene and hexamethanol as a solvent, the main reaction products are diethylphenylmalonate (20%), monoethylhomophthalate (10%), and homophthalimide (50%). The mechanism of formation of these products is shown in scheme (22).

For the synthesis of substituted malonic esters, direct alkylation of diethyl sodium malonate can be used, but the method is not entirely successful, as it often leads to by-products resulting from the dehydrohalogenation of alkyl halides. The elimination reaction can be avoided to some extent by using the conjugate addition of the Grignard reagent to the alkylidenemalonate, as in the synthesis tert-butylmalonate by addition of methylmagnesium iodide to isopropylidenemalonate (scheme (23)). The conjugate addition of Grignard reagents to α,β-unsaturated esters serves as the main reaction; it can be greatly accelerated in the presence of 1% (mol.) copper chloride (1). In particular, such organocopper reagents as LiMeCu and MeCuP (C 4 H 9 - n), selectively add to the β-carbon atom of α,β-unsaturated ketones, providing a potential extension of the method by reactions similar to those shown in scheme (23).

Alkylation of esters of β-keto acids can also be used to obtain derivatives of dicarboxylic acids (schemes (24) and (25)). In the general case, the products of these reactions undergo further transformations or, as shown in scheme (24), are used to obtain keto acids.

To obtain derivatives of esters of malonic acid, diethyl oxal can be used by carrying out Claisen ester condensation and subsequent thermal decarbonylation (scheme (26)). This is a fairly general method for introducing an ethoxycarbonyl group. The use of esters, such as diethyl succinate (Scheme (27)), can lead to the production of α-oxo derivatives of dicarboxylic acids by hydrolysis of the β-oxo polycarboxylic acid ester intermediate.

Alkyl derivatives of succinic acid can be obtained by alkylation of the dianion, in turn obtained from monoethylsuccinate; alkylation proceeds regiospecifically (scheme (28)) at the carbon atom adjacent to the ester group. Other a-alkyl derivatives of adipic and pimelic acids can be obtained by a more complex sequence of reactions (Scheme (29)), since in this case the anions easily enter Dieckmann's cyclization.

Reactions similar to scheme (28) can be used to synthesize esters of unsaturated dicarboxylic acids. For example, as a result of the reaction of a monolithium derivative of di- tert-butylglutarate with various ketones, esters of hydroxydicarboxylic acids are obtained in excellent yields (13).

Hydrolysis of esters (13) with simultaneous dehydration leads to unsaturated derivatives of glutaric acid, if substituents R 1 or R 2 are not aromatic in nature (scheme (30)). However, if one of these substituents is aromatic, then hydrolysis is accompanied not only by dehydration, but also by decarboxylation and leads to unsaturated monocarboxylic acids.

The Wittig reaction is the most important general method for the regiospecific synthesis of esters of α,β-unsaturated and polyene dicarboxylic acids. In a typical synthesis (scheme (31)) , as in many similar cases, the reaction product is a mixture cis- and trance-isomers, which in this particular case can be separated by fractional crystallization. The Wittig reaction is especially widely used in the synthesis of carotenoids; in some cases, derivatives of unsaturated dicarboxylic acids are used in these syntheses. As a typical example, we present the synthesis of natural bixin (Scheme (32)): the key intermediate 5-methoxycarbonyl-3-methylpenta- cis-2-grans-4-dienal (14), as shown in the scheme, condenses with ylide (15) under standard Wittig reaction conditions.

2.3. Michael reactions

The Michael reaction is used to prepare various di- and polycarboxylic acids. In this section, we will look at some typical examples of this reaction. The malonate anion adds to the esters and nitriles of α,β-unsaturated acids to form products that give glutaric acid derivatives upon hydrolysis (schemes (33)-(36)).

Glutaric acids can also be obtained by adding dianions of carboxylic acids to α,β-unsaturated esters (scheme (37)). The isobutyric acid dianion is prepared in tetrahydrofuran at 0° C. using two equivalents of base; the Michael addition is followed by trimethylsilylation of the product.

The complete synthesis of the (±)-avenaciolide fungicide included, as a key step, the preparation of a substituted bislactone (16) as a result of a process similar to the Michael reaction (Scheme (38)). At the last stages of this synthesis, the desired double bond was introduced by pyrolysis of the sulfoxide in the presence of succinic anhydride.

2.4. Oxidative Methods

Many important pathways leading to di- and polycarboxylic acids include oxidation; some methods have found practical application. For convenience, we consider separately the oxidation of aromatic and aliphatic substrates.

(1) Production of aromatic acids

To obtain aromatic di- and polycarboxylic acids, the oxidation of side chains of various aromatic compounds is widely used. Alkylbenzenes, such as isomeric xylenes, readily oxidize to the corresponding carboxylic acids under harsh conditions. The examples in Schemes (39) -(45) illustrate a set of oxidizing agents that can be used for this purpose.

Oxidation of phenanthalene (scheme (46)) serves as a convenient method for the synthesis of both biphenyl-2,2"-dicarboxylic acid and its dimethyl ester. Oxidation of various acyl haloacenaphthenes leads to the corresponding naphthalene α and hydrides, although there are noticeable differences in the ease of formation of anhydrides (scheme (47 )).

(2) Production of aliphatic acids

In the synthesis of dicarboxylic acids in this way, two oxidative processes can be distinguished: the first includes oxidative dimerization, the second involves the cleavage of a carbon-carbon bond, often in cyclic compounds (scheme (47)). Esters of succinic acid can be obtained by oxidative dimerization of enolate anions in the presence of copper (II) salts. The lithium enolate method (scheme (48)) is simpler and appears to be more general than the alternative organozinc method (scheme (49)). Both reactions resemble long-known methods of dimerization of stable anions, for example, diethyl malonate anions using iodine as an oxidizing agent (Scheme (50)).

Acetylene acids and their esters undergo oxidative dimerization in high yield in aqueous ethanol under the action of oxygen or air in the presence of ammonium chloride or copper. This reaction was used in the synthesis of corticrocin, the reaction, which proceeded in this case with an almost quantitative yield at room temperature, was carried out by oxygen uptake (scheme (51)).

Olefins can be oxidized to dicarboxylic acids (scheme (52)) different ways, and if there were no problems associated with solubility in organic solvents, the most convenient for this purpose would be potassium permanganate. These difficulties can be overcome to some extent if acetic anhydride is used as a solvent. However, in this case, the yields are reduced, and as shown in the example of oxidation according to scheme (53), side reactions can occur.

The use of crown ethers eliminates most of the problems, because these compounds are able to form complexes with metal salts, which leads to an increase in solubility in an organic medium and an increase in the reactivity of anions. For example, dpcn;slohexyl-18-crown-6 forms a benzene-soluble complex (17) with potassium permanganate, which provides an excellent oxidizing agent for organic substrates. In particular, it oxidizes cyclohexene in quantitative yield to adipic acid (scheme (54)). Apparently, there is no reason to assume that the mechanism of this oxidation differs from that acting in aquatic environments(schemes (55), (56)).

Phase transfer catalysis can be used to oxidize alkenes with aqueous potassium permanganate. Reactions of Nitrogen dissolved in the organic phase with inorganic spices in the aqueous phase, which are inhibited by HD separation, are often catalyzed by the addition of trace amounts of tetraalkylammonium or tetra-a-kyaphosphonium salts soluble in the organic phase. It is assumed that catalysis is carried out due to the ability of cations soluble in an organic solvent to repeatedly transfer anions into the organic phase in a form suitable for the reaction. This effect is called phase transfer catalysis.

Ozone treatment of olefins is generally carried out in organic solvents, often at low temperatures. The resulting ozonide (18), which is usually too unstable to be safely isolated, can be oxidized to carboxylic acids. In the oxidation of a cyclic olefin, the reaction product is a dicarboxylic acid (Scheme (57)). This two-step process can be simplified, as it has been shown that, in favorable cases, emulsions of cyclic olefins and alkaline hydrogen peroxide react gently with ozone and form α,co-dicarboxylic acids in good yields (scheme (58)).

Other carbocyclic compounds can also be oxidized to dicarboxylic acids. AT suitable solvent cyclic ketones are oxidized by molecular oxygen to dicarboxylic acids (scheme (59)). It has been shown that many solvents autoxidize under the reaction conditions; however, the use of hexametapol (HMPTA) reduces these side reactions to a minimum and makes it possible to obtain satisfactory product yields. As a rule, the most acidic S-N connection ketone to form an unstable intermediate peroxy anion. Complete oxidation, similar to scheme (59), was achieved by the action of nitric acid.

Noteworthy is another technique involving hydr 0 . lysis since it is a general method for the preparation of perfluoroalkanedicarboxylic acids from a,co-bis(methylthio)polyfluoroalkanes. Telomerization of tetrafluoroethylene in the presence of dimethyl disulfide and gregg-butyl peroxide as a catalyst leads to products of type (21) (scheme (65)). As can be seen from the diagram, these products (P= 2-5) are hydrolyzed with sulfuric acid in methanol to methyl esters of fluorinated dicarboxylic acids.

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About 3 million tons of adipic acid are produced annually. About 10% is used in Food Industry in Canada, EU countries, in the USA and in many CIS countries.

Foods rich in adipic acid:

Juices from concentrates

Industrial fruit jelly

chewing gum

General characteristics of adipic acid

Adipic acid, or as it is also called, hexanedioic acid, is a food additive E 355, which acts as a stabilizer (acidity regulator), acidifier and baking powder.

Adipic acid has the appearance of colorless crystals with a sour taste. It is produced by chemical means when cyclohexane reacts with nitric acid or nitrogen.

Currently, a detailed study of all the properties of adipic acid is underway. Determined that given substance- low toxicity. Based on this, the acid is classified as a third safety class. According to State Standard(dated January 12, 2005) Adipic acid has a minimal harmful effect on humans.

Adipic acid is known to have a positive effect on taste finished products. Influences the physical Chemical properties test, improve appearance finished product, its structure.

Used in the food industry:

• to improve the taste and physical and chemical parameters of finished products;
• for longer storage of products, to protect them from spoilage, is an antioxidant.

In addition to the food industry, adipic acid is also used in light industry. It is used for the production of various artificial fibers, such as polyurethane.

Manufacturers often use it in household chemicals. Adipic acid esters are used in skin care cosmetics. Also, adipic acid is used as a component for products designed to remove scale and deposits in household equipment.

Daily human need for adipic acid:

Adipic acid is not produced in the body, and it is also not a necessary component for its functioning. The maximum allowable daily dosage of acid is 5 mg per 1 kg of body weight. The maximum permitted dosage of acid in water and drinks is no more than 2 mg per 1 liter.

The need for adipic acid increases:

Adipic acid is not a vital substance for the body. It is used only to improve the nutritional quality and shelf life of finished products.

The need for adipic acid is reduced:

• in childhood;
• contraindicated in pregnancy and lactation;
• during the adaptation period after the illness.

Absorption of adipic acid

To date, the effect of a substance on the body has not been fully studied. It is believed that this dietary supplement can be consumed in limited quantities.

Acid is not completely absorbed by the body: a small part of this substance is broken down in it. Adipic acid is excreted from the body with urine and exhaled air.

Useful properties of adipic acid and its effect on the body:

Useful properties has not yet been found in the human body. Adipic acid has a positive effect only on the preservation of food, their taste characteristics.

Factors affecting the content of adipic acid in the body

Adipic acid enters our body along with food, as well as when using certain household chemicals. The acid content is also affected by the scope of activity. A high concentration of a substance entering Airways can irritate mucous membranes.

A large number of adipic acid can enter the body during the production of polyurethane fibers.

To avoid negative consequences for health, it is recommended to observe all the necessary precautions at the enterprise, adhere to sanitary standards. The maximum allowable value of the content of a substance in the air is 4 mg per 1 m 3.

Signs of excess adipic acid

There were no signs of adipic acid deficiency.

Federal Agency for Education

State educational institution of higher professional education

Samara State Technical University

Department:"Organic chemistry"

“SYNTHESIS OF ADIPIC ACID”

Course work

Completed:

Supervisor:

Samara, 2007

1. Introduction

1.1. Properties of adipic acid

1.2. The use of adipic acid

1.3. Synthesis of adipic acid

2. Literary review. Methods for obtaining dicarboxylic and polycarboxylic acids

2.1. Carboxylation and alkoxycarbonylation

2.2. Condensation reactions

2.3. Michael reactions

2.4. Oxidative Methods

3. Experimental technique

Bibliography

1. Introduction

1.1. Properties adipic acid

Adipic acid (1,4-butanedicarboxylic acid) HOOC(CH 2) 4 COOH, molecular weight 146.14; colorless crystals; m.p. 153°C, b.p. 265°C/100 mmHg Art.; easily sublimes; d 4 18 = 1.344; decomposition point 210-240°C;

() = 4.54 (160°С), 2.64 (193°С); ; , , . Solubility in water (g per 100 g): 1.44 (15°C), 5.12 (40°C), 34.1 (70°C). Solubility in ethanol, in ether - limited.

Adipic acid has all the chemical properties characteristic of carboxylic acids. Forms salts, most of which are soluble in water. Easily esterified to mono- and diesters. Forms polyesters with glycols. Salts and esters of adipic acid are called adipinates. When interacting with NH 3 and amines, adipic acid gives ammonium salts, which, upon dehydration, turn into adipamides. With diamines, adipic acid forms polyamides, with NH 3 in the presence of a catalyst at 300-400 ° C - adipodinitrile.

When adipic acid is heated with acetic anhydride, a linear polyanhydride is formed BUT [-CO (CH 2) 4 COO-] n H, during the distillation of which at 210°C an unstable cyclic anhydride (formula I) is obtained, which at 100°C again turns into a polymer. Above 225 °C, adipic acid cyclizes to cyclopentanone (II), which is more easily obtained by pyrolysis of calcium adipate.

In industry, adipic acid is obtained mainly by a two-stage oxidation of cyclohexane. At the first stage (liquid-phase oxidation with air at 142-145°C and 0.7 MPa), a mixture of cyclohexanone and cyclohexanol is obtained, separated by distillation. Cyclohexanone is used to produce caprolactam. Cyclohexanol is oxidized with 40-60% HNO 3 at 55°C (NH 4 VO 3 catalyst); the yield of adipic acid is 95%.

Adipic acid can also be obtained:

a) oxidation of cyclohexane with 50-70% HNO 3 at 100-200°C and 0.2-1.96 MPa or N 2 O 4 at 50°C;

b) oxidation of cyclohexene with ozone or HNO 3 ;

c) from THF according to the scheme:

d) carbonylation of THF to adipic anhydride, from which the acid is obtained by the action of H 2 O.

1.2. Application adipic acid

The main area of ​​application of adipic acid is the production of polyamide resins and polyamide fibers, and these markets have long been formed and are experiencing fierce competition from polyester and polypropylene.

The use of adipic acid in the production of polyurethanes is increasing. Now the growth rate of production and consumption of polyurethanes exceeds the growth rate of production and consumption of polyamides, especially polyamide fibers. For example, the demand for adipic acid from Western European polyurethane producers is constantly increasing, and today its growth rate is approximately 12-15% per year. However, demand for polyamide (nylon) for plastics is also on the rise, especially in the Asian region. This is explained by the fact that for the production of polyurethanes in the Asia-Pacific countries, polyethers are more often used, in the synthesis of which adipic acid does not take part, therefore up to 85% of adipic acid is used here in the production of polyamides. This feature has a ripple effect on the demand for adipic acid in the region, so the average annual growth rate of global demand for this product is projected at 3-3.5%. In Russia, there is no own production of adipic acid, although there are very favorable conditions for this: a developed raw material base (cyclohexanol, cyclohexanone, nitric acid), there are large consumers of end products (plasticizers, monomers). The prospective need for adipic acid for Russia is estimated at several tens of thousands of tons per year. In the Russian Federation, adipic acid is used for the production of plasticizers, polyamides, pharmaceuticals, and polyurethanes.

So, adipic acid is a strategically and economically important raw material in the production of polyhexamethylene adipamide (~ 90% of the acid produced), its esters, polyurethanes; food additive (gives a sour taste, in particular in the production of soft drinks). That is, products based on adipic acid are widely used in the production of polyamides, plasticizers, polyesters, polyester resins for PU, PU foam, in the industrial processing of glass, in the electronic and electrical industries, in the production of disinfectants, in the food and chemical-pharmaceutical industries, in obtaining varnishes and enamels, solvents, self-curing compositions.

1.3. Synthesis adipic acid

Into a 5 liter round bottom flask equipped with a mechanical stirrer, thermometer and separating funnel ca. In 1 l, place 2100 g (16.6 mol) of 50% nitric acid (specific gravity 1.32; in a fume hood). The acid is heated almost to boiling and 1 g of ammonium vanadate is added. Start the stirrer and slowly add 500 g (5 mol) of cyclohexanol through a separating funnel. First, 40-50 drops of cyclohexanol are added and the reaction mixture is stirred until the reaction starts (4-5 min), which becomes noticeable by the evolution of nitrogen oxides (Note 3). Then the reaction flask is placed in an ice bath, the contents of the flask are cooled until the temperature of the mixture reaches 55-60 0 C. After that, cyclohexanol is added as soon as possible, maintaining the temperature within the limits indicated above. Toward the end of the oxidation (after 475 g of cyclohexanol had been added), the ice bath was removed; sometimes the flask even has to be heated in order to maintain the required temperature and to avoid cyclization of the adipic acid.

Stirring is continued for another hour after the addition of the entire amount of cyclohexanol. The mixture is then cooled to 0, the adipic acid is filtered off with suction, washed with 500 ml of ice water and air dried overnight. The output of white crystals with so pl. 146-149 0 is 395-410g. By evaporation of the mother liquors, another 30-40 g of product with m.p. 141-144 0 С (note 4). Total yield of crude adipic acid: 415-440g, or 58-60% theoretical. (note 6). The resulting product is reasonably pure for most purposes; however, a purer product can be obtained by recrystallization of crude adipic acid from 700 ml of concentrated nitric acid sp. weight 1.42. cleaning losses are about 5%. Recrystallized adipic acid melts at 151-152 0 (Notes 6 and 7).

Notes.

1. It is suggested not to use a catalyst if the temperature of the reaction mixture, after the start of the reaction, is maintained at 85-90 0 (Hartman, private communication).

2. Used technical cyclohexanol, practically free of phenol. More than 90% of the product boiled within 158-163 0 .

3. It is very important that the oxidation begin before a significant amount of cyclohexanol is added, otherwise the reaction may become violent. The reaction must be carried out in a well-functioning fume hood.

4. Nitric acid mother liquors contain significant amounts of adipic acid mixed with glutaric and succinic acids. It turned out that the separation of these acids by crystallization is practically impractical. However, if nitric acid is removed by evaporation, and the remaining mixture of acids is esterified with ethyl alcohol, then a mixture of ethyl esters of succinic (bp. 121-126 0 /20mm), glutaric (bp. 133-138 0 /20mm) and adipic b.p. (142-147 0 /20mm) acids. These esters can be successfully separated by distillation.

5. The following modified recipe may give a better outcome. In a 3-liter flask equipped with a stirrer, a reflux condenser and a dropping funnel, fixed in asbestos stoppers impregnated with liquid glass, place 1900 ml of 50% nitric acid (1262 ml of nitric acid, sp. weight 1.42, diluted to 1900 ml) and 1 g of vanadate ammonium. The flask is placed in a water bath heated to 50-60 0 , and very slowly, with the stirrer running, 357 g (3.5 mol.) of technical cyclohexanol are added so that the bath temperature is maintained at 50-60 0 . This operation lasts 6-8 hours. The reaction is terminated by heating the water bath to boiling until the evolution of nitrogen oxides ceases (about 1 hour). The hot reaction mixture is siphoned off and allowed to cool. Yield of crude adipic acid: 372g (72% theoretical).

The invention relates to a method for producing adipic acid by oxidation of caprolactam, where caprolactam-containing waste from the production of caprolactam is used as a feedstock - distillation cubes from the production of caprolactam by oxidation of cyclohexane, with a caprolactam content of at least 90%, at a temperature of 75-100 ° C liquid medium, and the reaction is carried out using an oxidizing agent, which is a mixture of 30% hydrogen peroxide, taken in the amount of H 2 O 2 /CL (1-1.1) / 1 mol / mol, and concentrated sulfuric acid (96%) in the amount of 0, 2-0.36 mol/kg of the reaction mass, in which the oxidate is acidified with concentrated sulfuric acid in order to isolate adipic acid. EFFECT: use of industrial waste, higher yield, absence of hard-to-separate impurities in commercial adipic acid. 2 w.p. f-ly, 1 tab.

The invention relates to a method for the production of adipic acid, in which the waste products of caprolactam production by cyclohexane oxidation are used as raw materials: distillation stills (CD), representing distillation residues after caprolactam distillation, containing at least 90% caprolactam (the rest is organic impurities). With an average production capacity of 100 thousand tons/year of caprolactam, approximately 700-800 tons of CA are formed.

AT modern technology production of caprolactam, it is planned to return this waste after separation of oligomers back into the process to the rearrangement stage or to the extraction stage. Also known is the "Method for isolating caprolactam from the bottom products of its distillation", according to which the processing of bottom products of caprolactam distillation is carried out with a solution of caprolactam sulfate at 110-130 ° C or products of the Beckmann rearrangement at 40-80 ° C. However, as the results show, in this case, chemical transformations occur, in which some impurities decrease, but others appear. Consequently, the return of CD to the process leads to the recirculation of impurities and, as a consequence, to an additional load on the stages of extraction and ion-exchange purification, a partial loss of caprolactam at high temperatures under recirculation conditions. All this affects the quality of the polyamide obtained from caprolactam.

We offer new approach: remove distillation cubes from recycling by finding a way to process them into target products, which, in terms of physicochemical properties, radically differ from the properties of impurities present in caprolactam-containing waste and can be separated from them in a fairly pure form, for example, into adipic acid (AA).

Adipic acid is a technically demanded expensive product of organic synthesis, widely used in various fields. The main consumers are the production of polymers (polyamide) and plasticizers for PVC compositions. The market value of AA is 60-70 thousand rubles/t, plasticizers based on it are 90-150 thousand rubles/t (with the cost of caprolactam being 73 thousand rubles/t).

Currently, the main method for obtaining AA is the direct oxidation of hydrocarbons, most often cyclohexane or a mixture of cyclohexanol/cyclohexanone with air, an oxygen-containing gas in the presence and without catalysts and solvents.

These methods have disadvantages associated with the low selectivity of the process n/b 50-60%, the complexity of the selection and purification of commercial adipic acid from impurities and trace impurities.

The closest in composition to the claimed invention is a method for producing AK, in which the waste products of the production of caprolactam by the phenol method are used as raw materials: the head fractions of the rectification of cyclohexanol and cyclohexanone. The method includes their oxidation with 40-70% nitric acid, taken in an amount of 2-5 wt.h. per 1 wt.h. head fraction of cyclohexanol or cyclohexanone at a temperature of 40-70°C, distillation of unreacted cyclohexane or cyclohexene oxidate in the form of an aqueous azeotrope, cooling the reaction mass to 5-20°C, separating adipic acid, washing it with water and drying. To increase the yield of adipic acid, concentrated nitric acid is added to the oxidate until its content in the oxidate is 60-70%, and further oxidation of cyclohexane or cyclohexene is carried out at a temperature of 70-120°C and a pressure of 0.1-0.3 MPa. The advantage of the method is the use of industrial waste; however, the use of nitric acid leads to the emergence of new - difficult to utilize gas emissions containing nitrogen oxides; the selectivity of the process does not exceed 60-65%.

All of the above requires continued research: using everything valuable in early works, it is necessary to develop effective method obtaining adipic acid from industrial waste.

The objective of the present invention is to create a method for producing AA by oxidation of caprolactam contained in the waste products of caprolactam production from cyclohexane - distillation cubes. EFFECT: obtaining commercial grade adipic acid with a yield of n/m 70% from distillation cubes.

To solve the problem, distillation cubes, in which the content of caprolactam is more than 90%, were oxidized with a mixture of 30% hydrogen peroxide solution, taken in the amount of H 2 O 2 /CL=(1-1.1)/1 (mole) and sulfuric acid in the amount of 0.2-0.36 mol/kg of the reaction mass, at temperatures of 75-100°C. The addition of concentrated sulfuric acid is necessary for the hydrolysis of intermediate oxidation products: adipimide and adipic acid amide (reaction 2).

Oxidation Method:

30 g of distillation cubes containing 0.27 mol of caprolactam were loaded into a round-bottom flask with a stirrer, and a 30% solution of hydrogen peroxide was added, maintaining the ratio in the reaction mass H 2 O 2 /CL=(1-1.1)/1 (mol. ). When the reaction temperature was reached, concentrated sulfuric acid(96%) in the amount of 0.2-0.36 mol/kg of the reaction mass and began sampling. Samples were analyzed for caprolactam content (chromatographically) and hydrogen peroxide content titrimetrically. To determine the composition of the oxidation products of caprolactam, we developed an analysis procedure consisting in the esterification of the oxidation products with ethanol followed by a chromatographic analysis of the resulting esters.

Obtaining adipic acid by oxidation of caprolactam proceeds according to reactions (1-2):

The oxidation process can be carried out continuously or batchwise. At the end of the reaction, the oxidate is treated with sulfuric acid at the rate of 0.5 mol of acid per 1 mol of caprolactam, which allows, on the one hand, to isolate AA, and on the other hand, to recycle unoxidized or partially oxidized compounds (for example, adipimide and adipic acid amide). After washing, recrystallization and drying, the melting point of adipic acid was determined (t pl =155-155.5°C).

The advantages and features of the present invention can be seen from the examples which are given below by way of explanation. The results are shown in table 1.

Examples 1-3 were performed by varying the temperature from 75 to 100°C at a constant concentration of sulfuric acid of 0.23 mol/kg of the reaction mass in order to clarify the effect of temperature on the process. The process of oxidation of distillation cubes in the temperature range of 75-90°C (examples 1-2) proceeds slowly (30-28 hours), the conversion of caprolactam is 90-93%, the yield of adipic acid from theory does not exceed 58%. At a temperature of 100°C (example 3) for 14 hours at a conversion of 94%, the yield of AA is 81%.

Examples 4-7 are performed at a temperature of 100°C with varying the addition of sulfuric acid in the amount of 0-0.36 mol/kg. Analysis of the results shows that at 100°C and adding concentrated sulfuric acid in the amount of 0.2-0.23 mol/kg (examples 5-6) for 14-18 hours, the yield of AA is 75-81% with a caprolactam conversion of 94%; in the absence of sulfuric acid additives (example 4) caprolactam with a conversion of 95% is oxidized into intermediate products: adipimid and adipic acid amide; with an increase in the amount of sulfuric acid to 0.36 mol/kg (example 7) with a conversion of caprolactam of 93%, the yield of adipic acid decreases to 25%, which is explained by the appearance of a parallel hydrolysis reaction of caprolactam to aminocaproic acid.

Thus, the conditions for obtaining adipic acid are: the ratio of H 2 O 2:CL=(1-1.1)/1 (mol); the amount of concentrated sulfuric acid - 0.2-0.23 mol/kg of the reaction mass, t=75-100°C; at a caprolactam conversion of 94% and a temperature of 100°C, the yield of adipic acid from theory is 75-81%, t pl =155-155.5°C.

Compared with the prototype, the proposed method has a set of technical advantages: technologically simple, characterized by greater selectivity, the absence of hard-to-separate impurities in commercial adipic acid.

Indicators	Example number
1	2	3	4	5	6	7
Influence of the process temperature at a constant concentration of H 2 SO 4	Influence of the initial concentration of sulfuric acid at t=const
Process temperature, °С	75-80	90	100	100	100	100	100
Initial concentration of sulfuric acid in the reaction mass, mol/kg of the reaction mass	0,23	0,23	0,23	0	0,20	0,23	0,36
Reaction time, hour	32	28	14	20	18	14	12
CL conversion, %	90	93	94	95	94	94	93
AK yield from theory, %	53	58	81	0	75	81	25

3. French patents No. 2761984, 2791667, 2765930.

4. US Patent No. 5294739.

5. Patent RU 2296743 C2. France. Declared 01/27/2006; published 10.04.2007. "Method for the production of adipic acid".

6. Patent No. 93021182. Russia. Declared 05.11.1993; published 06/20/1996. "Method for the production of adipic acid".

7. Levanova S.V., Gerasimenko V.I., Glazko I.L. et al. // Journal of the Russian Chemical Society. D.I. Mendeleev. 2006. T. L. No. 3. P. 37-42.

CLAIM

1. A method for producing adipic acid by caprolactam oxidation, where caprolactam-containing wastes from caprolactam production are used as feedstock - distillation cubes from caprolactam production by cyclohexane oxidation, with a caprolactam content of at least 90%, at a temperature of 75-100 ° C in a liquid medium, characterized in that the reaction is carried out using an oxidizing agent, which is a mixture of 30% hydrogen peroxide, taken in an amount of H 2 O 2 /CL (1-1.1) / 1 mol / mol, and concentrated sulfuric acid (96%) in an amount of 0.2- 0.36 mol/kg of the reaction mass, in which the oxidate is acidified with concentrated sulfuric acid in order to isolate adipic acid.

2. The method according to claim 1, characterized in that the amount of concentrated sulfuric acid in the oxidizer should be 0.2-0.23 mol/kg of the reaction mass.

3. The method according to claim 1, characterized in that the oxidate is acidified with concentrated sulfuric acid (96%) in order to isolate adipic acid at the rate of 0.5 mol of acid per 1 mol of caprolactam.