Q.Write the structure of the repeat unit of terylene (polyethylene terephthalate), naming the type of linkage present.

Terylene is formed by condensing ethylene glycol, $\text{HO--CH}_2\text{CH}_2\text{--OH}$, with terephthalic acid, $p\text{-HOOC--C}_6\text{H}_4\text{--COOH}$; at each step, one $-\text{OH}$ condenses with one $-\text{COOH}$ to form an ester linkage, $-\text{CO--O}-$, releasing water. Repeating this across both ends of every monomer gives the repeat unit $\big[-\text{O--CH}_2\text{CH}_2\text{--O--CO--C}_6\text{H}_4\text{--CO--}\big]_n$, in which the flexible two-carbon glycol bridge alternates with the rigid, planar benzene-ring-containing terephthalate unit, joined thro …

Form the ester linkage between the diol's $-\text{OH}$ and the diacid's $-\text{COOH}$, and repeat across the bifu …

Writing an amide linkage instead of an ester linkage; omitting the benzene ring from the te …