OCR A-Level Chemistry Synthesis and analytical techniques (02), June 2025: Question 1

1 mark · Easy difficulty · Multiple Choice

Identify which given organic compound is both alicyclic and unsaturated.

Practise this question

Question

Multiple choice question asking: 'Which compound is alicyclic and unsaturated?' Four skeletal structures are presented: A is methylbenzene (toluene), an aromatic ring with a methyl group; B is a branched open-chain alkene; C is 1-methylcyclohexene, a six-membered ring containing a C=C double bond with an attached methyl group; D is methylcyclohexane, a fully saturated six-membered ring with a methyl group. An answer box is provided labeled 'Your answer' with a total mark of 1.
Question text

1 Which compound is alicyclic and unsaturated?

A

B

C

D

Your answer

[1]

Mark scheme

Show the mark scheme Mark scheme table row showing question number 1, correct answer 'C', and marks '1'.

1 C 1

How to answer it

Identifying Alicyclic and Unsaturated Hydrocarbons

What this question tests

This question assesses fundamental OCR A organic chemistry nomenclature and definitions from Module 4: Core Organic Chemistry:

  • Distinguishing between aliphatic, alicyclic, and aromatic compounds.
  • Distinguishing between saturated and unsaturated carbon skeletons.
  • Interpreting skeletal formulas for cyclic and acyclic molecules.
Question 1 Analysis [1 Mark]

Part 1: Multiple Choice Classification

Question Prompt: "Which compound is alicyclic and unsaturated?"

✅ Correct Answer

C

Mark Scheme: Award 1 mark for letter C.

Compound C is 1-methylcyclohexene. It contains a non-aromatic carbon ring (making it alicyclic) and at least one C=C double bond (making it unsaturated). Both conditions are fulfilled.

💡 Key Knowledge & Definitions

  • Alicyclic: An aliphatic compound arranged in non-aromatic ring structures, with or without side chains (e.g. cyclohexane, cyclopentene).
  • Aromatic: A compound containing a fully delocalised benzene ring (arene system).
  • Aliphatic: Carbon atoms joined together in straight chains, branched chains, or non-aromatic rings.
  • Unsaturated: Contains at least one multiple carbon–carbon bond (e.g., C=C double bond, C≡C triple bond).
  • Saturated: Contains only single C–C bonds.

📐 Step-by-Step Breakdown of Options

Option Name / Structure Ring Type Saturation Matches Both Criteria?
A Methylbenzene (toluene) Aromatic (benzene ring) Unsaturated (arene) ❌ No (It is aromatic, not alicyclic)
B 4-methylhex-2-ene Aliphatic (acyclic) (open chain) Unsaturated (C=C present) ❌ No (It has no ring)
C 1-methylcyclohexene Alicyclic (6-membered ring) Unsaturated (C=C present) ✅ YES (Both criteria met)
D Methylcyclohexane Alicyclic (6-membered ring) Saturated (only C–C single bonds) ❌ No (It is saturated)

🧠 Exam Technique: Two-Condition Matrix

When a multiple-choice question requires two specific properties (here: alicyclic AND unsaturated), systematically eliminate incorrect options one condition at a time:

  1. Filter by "Alicyclic": Cross out open-chain compounds (B) and aromatic benzene rings (A). This immediately eliminates 50% of the choices!
  2. Filter by "Unsaturated": Look at remaining candidates (C and D). Check for a double bond. Structure C contains a C=C bond; Structure D has only single bonds.

❌ Common Errors & Pitfalls

  • Confusing Alicyclic with Aromatic: Students frequently mistake benzene-containing rings (like in A) as alicyclic simply because they are cyclic. Benzene rings are strictly classified as aromatic.
  • Misreading the Drawing in B: The skeletal chain in B is drawn bent in a 'U' shape, leading some students to hastily perceive it as a closed ring. Check that the vertices actually connect into a closed loop!
  • Overlooking Saturation in D: Selecting D because it is cyclic, while forgetting to verify whether it contains a double bond.

Topics

Module 4: Core organic chemistry · 4.1 Basic concepts and hydrocarbons

Question and mark scheme from the OCR A-Level Chemistry examination, Synthesis and analytical techniques (02), June 2025. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.