Question

Polyethylene terephthalate is also prepared by the transesterification of dimethyl terephthalate with ethylene glycol. Draw the mechanism for this nucleophilic acyl substitution.

Short answer

Answer

Mechanism of the reaction

Step-by-step solution

Polyethylene terephthalate

The short form for polyethylene terephthalate is PET. This is a polymeric material used in the synthesis of plastics. The plastic produced by this polymer is widely used in food packaging.

Transesterification

The chemical reaction that happens between the oil and alcohol leading to the formation of esters and glycerol is called a transesterification reaction.

Mechanism of the given reaction

The water molecule reacts with dimethyl terephthalate resulting in the formation of the structure containing a positive charge on the oxygen atom. Water molecule is added again. The steps are repeated several times.

The mechanism is shown below.

Mechanism of the reaction