OCR A-Level Chemistry Synthesis and analytical techniques (02), November 2020: Question 3

1 mark · Medium difficulty · Multiple Choice

Identify which of the given reagents will not react with HOCH2CH2CH2COOH.

Practise this question

Question

Multiple choice question asking which reagent will not react with HOCH2CH2CH2COOH. The options are A: NaCN in ethanol, B: C2H5OH in the presence of an acid catalyst, C: (CH3CO)2O, D: concentrated H2SO4. There is a box for the answer and a mark allocation of [1] at the bottom right.
Question text

3 Which of these reagent(s) will not react with HOCH2CH2CH2COOH?

A NaCN in ethanol

B C2H5OH in the presence of an acid catalyst

C (CH3CO)2O

D concentrated H2SO4

Your answer

[1]

Mark scheme

Show the mark scheme Mark scheme table showing question number 3 with correct answer A, worth 1 mark.

3 A 1 1.1

How to answer it

Reactions of Bifunctional Organic Compounds

What this question tests

This question assesses your ability to identify functional groups within a bifunctional molecule ( HOCH₂CH₂CH₂COOH , containing both an alcohol and a carboxylic acid group) and recall the specific chemical reactions associated with each functional group, including nucleophilic substitution limits, esterification, and acid-catalysed dehydration.

Question 3 Multiple Choice

Analyzing Functional Group Reactivity

The target molecule is HOCH₂CH₂CH₂COOH (4-hydroxybutanoic acid). It possesses two distinct reactive handles:

  • An aliphatic carboxylic acid group ( -COOH )
  • A primary alcohol group ( -OH )

✅ Correct Answer: A

NaCN in ethanol will not react with 4-hydroxybutanoic acid. Halogenoalkanes undergo nucleophilic substitution with cyanide ions to form nitriles, but simple aliphatic alcohols and carboxylic acids do not react with sodium cyanide.

💡 Key Knowledge: Why B, C, and D React

  • B ( C₂H₅OH + acid catalyst): Reacts with the -COOH group via esterification to form an ester.
  • C ( (CH₃CO)₂O ): Ethanoic anhydride reacts with the primary -OH alcohol group to form an ester.
  • D (Concentrated H₂SO₄ ): Acts as a dehydrating agent, promoting elimination of water from the alcohol group (or promoting polyesterification/intramolecular cyclisation).

🧠 Exam Technique

When faced with a "will not react" multiple-choice question featuring a bifunctional molecule, systematically test each option against both functional groups. Eliminate options that trigger a known reaction.

❌ Common Errors

Students often misidentify carboxylic acid derivatives or assume that any carbon-containing reagent can attack a molecule containing an oxygen-based functional group. Always check for standard functional group interconversions learned in organic synthesis modules.

Mark Allocation: 1 mark for selecting A. (Specification reference 1.1)

Topics

Module 4: Core organic chemistry · Module 6: Organic chemistry and analysis · 6.1 Aromatic compounds, carbonyls and acids · 4.2 Alcohols, haloalkanes and analysis

Question and mark scheme from the OCR A-Level Chemistry examination, Synthesis and analytical techniques (02), November 2020. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.