Identify a monomer used to prepare nylon 6,6 along with hexamethylene-diamine.

Step-by-step solution

Nylon 6,6 is a condensation polymer formed by the reaction of hexamethylenediamine and adipic acid under high pressure and at high temperature. The reaction involves the elimination of water molecules to form amide linkages. The monomers of Nylon 6,6 are hexamethylenediamine ( H₂N-(CH₂)₆-NH₂ ) and adipic acid ( HOOC-(CH₂)₄-COOH ). Answer: adipic acid