Adipic acid (there is another name for this substance - 1,4-butanedicarboxylic acid, the systematic name is hexanedioic acid) is the ultimate dibasic carboxylic acid. It has the following chemical formula: HOOC (CH2) 4COOH and gross formula C6O4H10. It has the same chemical properties as carboxylic acids. It forms salts, many of which are soluble in water (H2O). Etherified in di- and monoesters. Hexanedioic acid forms polyesters with glycols.
Adipic Acid Properties
1. The molar mass is 146.1 grams / mol.
2. The density is 1.36 grams / mol.
3. Limited soluble in ethanol, diethyl alcohol and acetone.
4. Solubility in water (H2O) is: at 15 degrees - 1.44 g in 100 g of water; at 40 degrees - 5.12 g; at 70 degrees - 34.1 g.
Thermal Properties of Hexadioic Acid
1. The melting point is 153 ° C.
2. The decomposition temperature is 210 - 240 ° C.
3. The boiling point (at 100 mmHg) is 265 ° C.
4. The decarboxylation temperature is 300-320 ° C.
5. The enthalpy of combustion is -2800 kJ / mol.
6. The enthalpy of melting is 16.7 kJ / mol.
7. The enthalpy of evaporation is 18.7 kJ / mol.
How is adipic acid obtained?
In industry, this substance is obtained mainly through the two-stage oxidation of cyclohexane. First, a mixture of cyclohexanol and cyclohexanone is obtained, which is then separated by distillation. Subsequently, cyclohexanone is used to produce caprolactam, and cyclohexanol is oxidized with 40-60% HNO3 (nitric acid). With this method, the yield of adipic acid is about ninety-five percent.
One of the promising methods for producing adipic acid is butadiene hydrocarbonylation.
What other methods are used to produce carboxylic acids, such as adipic acid? It can also be obtained by oxidizing cyclohexane with nitric acid (HNO3) at a temperature of + 100-200 ° C, diazotetraoxide (N2O4) at a temperature of +50 ° C or ozone (O3).
Adipic acid is also obtained by carbonylation of THF (tetrahydrofuran) to adipic acid anhydride, from which the substance under consideration is then obtained.
The use of adipic acid:
- this substance is a raw material (about ninety percent of all acid produced is used) in the production of polyhexamethylene adipinamide, as well as its polyurethanes and esters;
- it is used as a food additive (registered under the number E 355) to give the products a sour taste (including the production of soft drinks);
- adipic acid is the main component of descaling agents;
- used to remove material that remains after filling the joints between ceramic tiles;
- the use of carboxylic acids, such as adipic acid, is important for the preparation of intermediate synthesis products.
What chemical reactions does adipic acid enter?
1. This substance, when reacted with various metals, their basic hydroxides and oxides, gives the corresponding salts.
2. May displace weaker acid from its salt.
3. In the presence of an acidic catalyst, adipic acid reacts with alcohols. In this case, esters are formed .
4. When heating the ammonium salts of adipic acid, their amides are formed.
5. Under the influence of SOCl2, adipic acid is converted to the corresponding acid chloride.
Adipic acid esters
1. Methyl adipate is used for the electrochemical synthesis of dimethyl sebacinate.
2. Diallyl adipate is a hardener of polyester resins.
3. Ethyl adipate is used as an additive to leaded gasoline in order to increase its octane number.
4. Diethyl adipate is used as a plasticizer in the production of food films, shoes, PVC, artificial leather, children's toys, linoleum, stretch ceilings.
5. Diisopropyladipate is used as a component of skin cosmetics.