Q.Identify the monomer in the following polymeric structures.

(i) $-[-C(=O)-(CH_2)_8-C(=O)-NH-(CH_2)_6-NH-]_n-$

This repeat unit is that of Nylon-6,10, formed by condensation of two bifunctional monomers:

• Sebacic acid: $HOOC-(CH_2)_8-COOH$ (10 carbons total, contributing the $-C(=O)-(CH_2)_8-C(=O)-$ portion)
• Hexamethylenediamine: $H_2N-(CH_2)_6-NH_2$ (contributing the $-NH-(CH_2)_6-NH-$ portion) with loss of water at each amide linkage.

(ii) The six-membered triazine ring bearing $-NH-$ and $-NH-CH_2-$ substituents, linked by $-CH_2-$ bridges

This repeat unit is characteristic of melamine-formaldehyde resin, formed by condensation of:

• Melamine (2,4,6-triamino-1,3,5-triazine), the triazine ring bearing three $-NH_2$ groups
• Formaldehyde: $HCHO$ …

For each repeat unit, identify the recurring amide/methylene-bridge linkage pattern, count the carbon spacer lengths to fix the specific acid/di …

• Confusing sebacic acid (8 CH2 groups between the two -COOH carbons) with adipic acid (4 CH2 groups, used in Nylon-6,6) — the carbon count matters. …