Question

Nomex, another aromatic polyamide (compare aramid), is prepared by polymerization of 1,3 -benzenediamine and the diacid chloride of 1,3 -benzenedicarboxylic acid. The physical properties of the polymer make it suitable for high-strength, high-temperature applications such as parachute cords and jet aircraft tires. Draw a structural formula for the repeating unit of Nomex.

Short answer

Answer: The structural formula of the repeating unit of Nomex is NH-benzene-ring (NHCO) - benzene. It consists of two benzene rings connected by an amide bond (-CONH-), maintaining a 1,3-substitution pattern.

Step-by-step solution

Draw 1,3-benzenediamine structure

To draw the structure of 1,3-benzenediamine, start with a benzene ring (a six-membered ring with alternating double bonds) and then add an amino group (NH2) to the first and third carbon atoms.

Draw diacid chloride of 1,3-benzenedicarboxylic acid structure

To draw the structure of the diacid chloride of 1,3-benzenedicarboxylic acid, begin with a benzene ring and then add a carboxylic acid chloride functional group (COCl) to the first and third carbon atoms.

Condensation reaction between monomers

Now, perform a condensation reaction between the amine groups on 1,3-benzenediamine and the acid chloride groups on the diacid chloride of 1,3-benzenedicarboxylic acid. Each amine group (NH2) will react with an acid chloride group (COCl) to form an amide bond (CONH) and release a molecule of hydrogen chloride (HCl). To form the repeating unit, consider only one amino group reacting with one acid chloride group: NH2 --- benzene-ring --- NH2 + ClOC --- benzene-ring --- OCl -> HCl + NH --- benzene-ring (NHCO) --- benzene ---

Draw the repeating unit of Nomex

Based on the reaction in step 3, we can now draw the repeating unit of Nomex. The repeating unit consists of two benzene rings connected by an amide bond (-CONH-). Since each benzene ring has two substituents, maintain the 1,3-substitution pattern like this: NH --- benzene-ring (NHCO) --- benzene ---