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Polycarbonates are similar to polyesters, except their carbonyl group is bonded to two alkoxy or aryloxy groups. Lexan is synthesized by reacting phosgene with bisphenol A in the presence of pyridine. Lexan is a tough, transparent material used in applications such as bullet-resistant windows, traffic-light covers, compact discs, and motorcycle helmets. Lexan belongs to which class of polymers?

1. Polycarbonate polymer
2. Polyester polymer
3. Polyamide polymer
4. Phenol-formaldehyde polymer

Correct answer: Polycarbonate polymer

Solution

Lexan is a polycarbonate polymer. The reaction of phosgene (COCl2) with bisphenol A (a diol) forms repeating -O-CO-O- (carbonate) linkages. This is explicitly stated in the problem — polycarbonates have their carbonyl linked to two alkoxy/aryloxy groups, which is the defining feature of the carbonate group.

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