A short fragment of a polymer chain (four repeat units, end groups shown, methyl groups drawn with wedges) is drawn. Select all correct statements.

AEvery diad in the fragment is meso
BSuch regular chains give a more crystalline, higher-melting polymer than the atactic form
CThis is the main product of free radical polymerisation of the monomer
DIt can be obtained with a Ziegler-Natta catalyst

Answer: A, B, D

All neighbouring stereocentres have the same relative configuration, so every diad is meso and the polypropylene is isotactic. Such regular chains pack well, giving a crystalline, higher-melting material than the atactic polymer, and Ziegler-Natta catalysts produce it. Free radical polymerisation gives mainly atactic polymer, so C is wrong.

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A short fragment of a polymer chain (four repeat units, end groups shown, methyl groups drawn with wedges) is drawn. Select all correct statements.

Answer: A, B, D

More questions on Geometry, tacticity and crosslinking in drawn chains