Cambridge OCR A Level · Chemistry B (Salters) - H433

Reaction mechanisms: Practice Questions

2 multiple-choice questions marked as you go, and 5 written questions with worked solutions. All on Reaction mechanisms.

7 questions20 marksFree, no account

Question 1

1 mark

In the mechanism for the electrophilic addition of hydrogen bromide to ethene, what is the nature of the intermediate formed?

Question 2

1 mark

The reaction of propene with hydrogen bromide yields two different bromoalkane products. Which statement correctly describes the mechanism that leads to the major product, 2-bromopropane?

Question 3

2 marks

In the electrophilic addition mechanism of bromine to ethene, what does a curly arrow starting from the \(C=C\) double bond towards the \(Br-Br\) bond represent?

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Question 4

3 marks

In the radical chain reaction between methane and chlorine, the propagation stage involves two steps. Write the equation for the first propagation step involving a chlorine radical.

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Question 5

5 marks

Contrast the mechanisms of electrophilic substitution in arenes and electrophilic addition in alkenes, specifically explaining why benzene does not typically undergo addition.

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Question 6

3 marks

Ethene, \(C_2H_4\), reacts with hydrogen bromide, \(HBr\), to form bromoethane.

(a) Name the type of mechanism involved in this reaction.
(b) Describe the steps of the mechanism, including the use of curly arrows and partial charges (\(\delta+\) and \(\delta-\)).
(c) Explain why this reaction is classified as an addition reaction.

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Question 7

5 marks

The hydrolysis of halogenoalkanes is a nucleophilic substitution reaction. Consider the reaction of 1-chlorobutane with aqueous sodium hydroxide.

(a) Define the term nucleophile.
(b) Outline the \(S_N2\) mechanism for this reaction using curly arrows and partial charges to show the movement of electron pairs.
(c) Explain why the C-Cl bond is polar.

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