Q.Describe how terylene (Dacron) is manufactured from ethylene glycol and terephthalic acid, and state what type of polymer it is.

Terylene (Dacron, PET) is manufactured by heating ethylene glycol, $\text{HO--CH}_2\text{CH}_2\text{--OH}$, with terephthalic acid, $p\text{-HOOC--C}_6\text{H}_4\text{--COOH}$, in the presence of a catalyst (e.g. zinc acetate/antimony trioxide) at $420$--$460\ \text{K}$. At each step, one $-\text{OH}$ of the glycol condenses with one $-\text{COOH}$ of the diacid to form an ester linkage, $-\text{CO--O}-$, releasing water:

$n\,\text{HO--CH}_2\text{CH}_2\text{--OH} + n\,p\text{-HOOC--C}_6\text{H}_4\text{--COOH} \rightarrow \big[-\text{O--CH}_2\text{CH}_2\text{--O--CO--C}_6\text{H}_4\text{--CO--}\big]_n + 2n\,\text{H}_2\text{O}$ …

Identify the reactive $-\text{OH}$ and $-\text{COOH}$ groups on the two monomers, form the ester linkage between them …

Confusing terylene's ester linkage with nylon's amide linkage; forgetting terephthalic acid is a …