OCR A-Level Chemistry Synthesis and analytical techniques (02), June 2019: Question 8

1 mark · Medium difficulty · Multiple Choice

Identify the least likely organic product when phenol reacts with bromine from the given multiple-choice options.

Practise this question

Question

Multiple-choice question 8 asking which is the least likely organic product when phenol reacts with bromine. Four options A, B, C, and D show benzene rings with an -OH group and various numbers and positions of bromine substituents: A has 2 bromine atoms at positions 3 and 5 relative to the OH group; B has 2 bromine atoms at positions 2 and 6; C has 2 bromine atoms at positions 2 and 3; D has 3 bromine atoms at positions 2, 4, and 6 (2,4,6-tribromophenol).
Question text

8 Phenol reacts with bromine.

Which is the least likely organic product?

OH

Br

A

Br

OH

Br Br

B

OH

Br

C

Br

OH

Br Br

D

Br

Your answer

[1]

Mark scheme

Show the mark scheme Mark scheme indicating the correct answer for question 8 is C, worth 1 mark.

8 C 1 AO1.2

How to answer it

Phenol Reacting with Bromine

What this question tests

This question assesses your knowledge of the directing effects of functional groups on a benzene ring (specifically the activating and 2,4,6-directing nature of the hydroxyl group in phenol), as well as your ability to interpret structural isomers of brominated organic products.

Question Multiple-Choice Analysis

Exam Question Overview

Students are asked to identify which of the four given structures is the least likely organic product when phenol reacts with bromine.

✅ Correct Answer: C

Structure C places two bromine atoms at adjacent positions (positions 2 and 3 relative to the -OH group). This is sterically unfavourable and does not match the symmetric activating directing pattern of phenol.

💡 Key Knowledge

  • The -OH group in phenol is strongly activating.
  • It directs incoming electrophiles (like Br₂) specifically to the 2, 4, and 6 positions due to the delocalisation of a lone pair from oxygen into the pi-system.
  • Bromination of phenol readily yields 2,4,6-tribromophenol without needing a halogen carrier catalyst.

🧠 Exam Technique

Read multiple-choice questions extremely carefully—this asks for the least likely product. Number the carbon atoms on the benzene ring starting with carbon-1 attached to the -OH group to quickly verify substituent positions.

❌ Common Errors

Students often mistake activating/deactivating groups or miscount carbon ring positions under exam stress, selecting fully brominated symmetric structures like D by mistake because they misread "least likely" as "most likely".

Mark Allocation: [1] mark available for choosing C (AO1.2 - Demonstration of knowledge and understanding).

Topics

Module 6: Organic chemistry and analysis · 6.1 Aromatic compounds, carbonyls and acids

Question and mark scheme from the OCR A-Level Chemistry examination, Synthesis and analytical techniques (02), June 2019. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.