DP Chemistry (last assessment 2024)

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Question 22N.2.hl.TZ0.b

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Date November 2022 Marks available [Maximum mark: 1] Reference code 22N.2.hl.TZ0.b
Level hl Paper 2 Time zone TZ0
Command term Justify, Suggest Question number b Adapted from N/A
b.
[Maximum mark: 1]
22N.2.hl.TZ0.b

2-Bromobutane can react with cyanide, CN−, in a nucleophilic substitution reaction.

Suggest, with a reason, whether the reaction follows an SN1 or SN2 mechanism if only one stereoisomer was obtained as a product.

[1]

Markscheme

SN2 AND SN2 «mechanism» occurs with inversion of configuration

OR

SN2 AND SN1 «mechanism» would create a racemic mixture ✔

 

Accept appropriate diagrams.

Examiners report

Again the average mark was <50%, which resulted, probably equally, from students being unaware of the stereochemical implications of the SN1 and SN2 mechanisms and from an inability to express this understanding clearly.

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