DP Chemistry (last assessment 2024)

Test builder »

Question 18M.2.hl.TZ1.7

Select a Test
Date May 2018 Marks available [Maximum mark: 7] Reference code 18M.2.hl.TZ1.7
Level hl Paper 2 Time zone TZ1
Command term Compare and contrast, Deduce, Outline, State, Suggest Question number 7 Adapted from N/A
7.
[Maximum mark: 7]
18M.2.hl.TZ1.7

This question is about the reactions of halogenoalkanes.

(a)

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]

(b)

Outline why the rate of reaction of the similar bromo-compounds is faster.

[1]

Markscheme

C–Br bond weaker than C–Cl bond

 

Accept “Br– is a better leaving group”.

Do not accept "bromine is more reactive".

Do not accept “C–Br bond is longer than C–Cl” alone.

[1 mark]

(c.i)

State the organic product of the reaction between 1-chlorobutane, CH3CH2CH2CH2Cl, and aqueous sodium hydroxide.

[1]

Markscheme

butan-1-ol/CH3CH2CH2CH2OH

 

Do not accept “butanol” for “butan-1-ol”.

Accept “1-butanol”.

Do not penalize for name if correct formula is drawn.

[1 mark]

(c.ii)

Suggest how this product could be synthesized in one step from butanoic acid.

[1]

Markscheme

«reduction with» lithium aluminium hydride/LiAlH4

 

Do not accept “sodium borohydride/NaBH4”.

[1 mark]

(c.iii)

Deduce the name of the class of compound formed when the product of (c)(i) reacts with butanoic acid.

[1]

Markscheme

ester

[1 mark]

Syllabus sections