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Question 18M.2.hl.TZ1.a

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Date May 2018 Marks available [Maximum mark: 3] Reference code 18M.2.hl.TZ1.a
Level hl Paper 2 Time zone TZ1
Command term Compare and contrast Question number a Adapted from N/A
a.
[Maximum mark: 3]
18M.2.hl.TZ1.a

This question is about the reactions of halogenoalkanes.

Compare and contrast the mechanisms by which 1-chlorobutane, CH3CH2CH2CH2Cl, and 2-chloro-2-methylpropane, (CH3)3CCl, react with aqueous sodium hydroxide, giving two similarities and one difference.

 

[3]

Markscheme

Any two similarities:

heterolytic bond breaking

OR

chloride ions leave

 

nucleophilic/OH– substitution

both first order with regard to [halogenoalkane]

 

One difference:

CH3CH2CH2CH2Cl is second order/bimolecular/SN2 AND (CH3)3CCl is first order/unimolecular/SN1

OR

CH3CH2CH2CH2Cl rate depends on [OH–] AND (CH3)3CCl does not

OR

CH3CH2CH2CH2Cl is one step AND (CH3)3CCl is two steps

OR

(CH3)3CCl involves an intermediate AND CH3CH2CH2CH2Cl does not

OR

CH3CH2CH2CH2Cl has inversion of configuration AND (CH3)3CCl has c. 50 : 50 retention and inversion

 

Do not accept “produces alcohol” or “produces NaCl”.

Accept “substitution in 1-chlorobutane and «some» elimination in 2-chloro-2-methylpropane”.

[3 marks]

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