Alkenes exam questions

Question 1

Explain why there is an attraction between a C=C double bond and Br2 3 marks

Answer 1

C=C is a region of high electron density
Br-Br becomes polarised
BrS+ becomes attracted to the C=C

Question 2

State what you would observe if bromine water was added to poly(chloroethene) 2 marks

Answer 2

No reaction/ Yellow- brown
Explanation- Polychloroethene is saturated, no double carbon bonds in the hydrocarbon chain

Question 3

Explain why more of isomer E than isomer F is formed in this reaction. 2 marks

Answer 3

E is formed via a more stable carbocation
2y carbocation is more stable than 1y carbocation

Question 4

Which statement is not correct about CH2═C(CH3)CH2Br?
A It displays E-Z isomerism.
B It forms an addition polymer.
C It reacts with electrophiles.
D It decolourises bromine water.
1 mark

Answer 4

A

Question 5

Which alkene reacts with hydrogen bromide to give 2-bromo-3-methylbutane as
the major product?
A (CH3)2C=CHCH3
B CH3CH2CH=CHCH3
C CH3CH2C(CH3)=CH2
D (CH3)2CHCH=CH2

Answer 5

D

Question 6

Which statement is correct about poly(chloroethene)?
A It has the empirical formula CHCl
B It decolourises bromine water.
C Its brittleness is reduced by plasticisers.
D Its polymer chain contains alternate single and double
bonds.

Answer 6

C