DP Chemistry (last assessment 2024)

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Question 18N.3.sl.TZ0.b

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Date November 2018 Marks available [Maximum mark: 1] Reference code 18N.3.sl.TZ0.b
Level sl Paper 3 Time zone TZ0
Command term Describe Question number b Adapted from N/A
b.
[Maximum mark: 1]
18N.3.sl.TZ0.b

While heating solid cholesteryl benzoate, Reinitzer discovered the liquid crystal phase.

The structure of biphenyl nitrile is shown.

Describe, giving a reason, a feature of the molecular structure, other than its polarity, that allows biphenyl nitrile to show liquid crystal behaviour.

[1]

Markscheme

ALTERNATIVE 1:

«bulky/long» C5H11/R/alkyl «group/chain» AND prevents molecules from packing closer together «to form solid state» ✔

 

ALTERNATIVE 2:

biphenyl «fragment»/two benzene rings/two aromatic rings AND «makes molecule» rigid/rod-shaped ✔

 

Accept “rigid/rod-shaped molecule, so aligns with other molecules” for ALTERNATIVE 2.

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