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CAIE A-Level Chemistry AS 14.2 Alkenes Questions

Practise alkene preparation, electrophilic addition, oxidation and structural deductions from reaction products.

Syllabus
2028–2030
Course
Chemistry 9701
Level
AS

Exam points

  • select reagents and conditions for addition or oxidation across the C=C bond
  • use curly arrows and intermediates to complete electrophilic-addition mechanisms
  • deduce an alkene structure from oxidative-cleavage products or a multi-step synthesis route

Covered syllabus points

14.2.1—Preparation of alkenes14.2.2—Reactions of alkenes14.2.3—Of aq. bromine to show the presence of a C=C14.2.4—Mechanism: electrophilic addition in alkenes,14.2.5—Inductive effects of alkyl groups

Question 1

[Maximum number: 1]

When heated with KOH dissolved in ethanol, halogenoalkanes can undergo an elimination reaction to form alkenes.

What are the possible elimination products when 2-bromobutane is heated with KOH dissolved in ethanol?

A

CH3CH=CHCH3\mathrm{CH}_{3} \mathrm{CH}=\mathrm{CHCH}_{3} only

B

CH3CH2CH=CH2\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}=\mathrm{CH}_{2} only

C

CH3CH=CHCH3\mathrm{CH}_{3} \mathrm{CH}=\mathrm{CHCH}_{3} and CH3CH2CH=CH2\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}=\mathrm{CH}_{2}

D

CH3CH=CHCH3\mathrm{CH}_{3} \mathrm{CH}=\mathrm{CHCH}_{3} and CH2=CHCH=CH2\mathrm{CH}_{2}=\mathrm{CHCH}=\mathrm{CH}_{2}

Question 2

[Maximum number: 1]

A molecule of geraniol is shown.

geraniol

geraniol

What is formed when geraniol is reacted with an excess of cold dilute acidified MnO4−\mathrm{MnO}_{4}^{-}?

A
Figure for Question 2 — CAIE A-Level Chemistry AS — Option A
B
Figure for Question 2 — CAIE A-Level Chemistry AS — Option B
C
Figure for Question 2 — CAIE A-Level Chemistry AS — Option C
D
Figure for Question 2 — CAIE A-Level Chemistry AS — Option D

Question 3

[Maximum number: 1]

Which compound will decolourise Br2(aq)\mathrm{Br}_{2}(\mathrm{aq}) ?

A

CH3CH2CH2CH2CH2CO2H\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CO}_{2} \mathrm{H}

B

CH3CH2CH2CH2CH2CHO\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CHO}

C

CH3CHCHCH2CH2CH2OH\mathrm{CH}_{3} \mathrm{CHCHCH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{OH}

D

CH3CH2CH2CO2CH2CH3\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CO}_{2} \mathrm{CH}_{2} \mathrm{CH}_{3}

Question 4

[Maximum number: 1]

Bromine reacts with alkenes by an electrophilic addition mechanism in which a cation is formed as an intermediate.

Which mixture will produce the most stable intermediate cation?

A

3,3-dimethylpent-1-ene + bromine

B

ethene + bromine

C

methylpropene + bromine

D

propene + bromine

Question 5

[Maximum number: 1]

What is the correct name of the major product of the reaction of HBr with 3-ethylhex-3-ene?

A

3-bromo-3-ethylhexane

B

3-bromo-4-ethylhexane

C

4-bromo-3-ethylhexane

D

4-bromo-4-ethylhexane

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