OCR A-Level Chemistry Synthesis and analytical techniques (02), November 2021: Question 6

1 mark · Medium difficulty · Multiple Choice

Identify the two organic products formed when CH3CH2COOCH3 is heated with aqueous sodium hydroxide.

Practise this question

Question

Multiple choice question 6 asking for the two organic products when CH3CH2COOCH3 is heated with aqueous sodium hydroxide, with options A (CH3CH2COOH and CH3OH), B (CH3CH2COONa and CH3OH), C (CH3CH2COOH and CH3ONa), and D (CH3CH2COONa and CH3ONa).
Question text

6 CH3CH2COOCH3 is heated with aqueous sodium hydroxide to produce two organic products.

What are the two organic products?

A CH3CH2COOH and CH3OH

B CH3CH2COONa and CH3OH

C CH3CH2COOH and CH3ONa

D CH3CH2COONa and CH3ONa

Your answer

[1]

Mark scheme

Show the mark scheme Mark scheme indicating the correct answer is B for question 6, worth 1 mark.

6 B 1 AO1.2

How to answer it

Alkaline Hydrolysis of Esters

What this question tests

This question assesses your understanding of the alkaline hydrolysis (base-catalyzed hydrolysis) of esters using aqueous sodium hydroxide. It tests your knowledge of functional group reactions, specifically how esters react under reflux with alkali to yield a carboxylate salt and an alcohol, rather than a carboxylic acid.

Question 6 Multiple Choice

Alkaline Hydrolysis Products

✅ Correct Answer: B

CH₃CH₂COONa and CH₃OH

Alkaline hydrolysis using aqueous NaOH produces a carboxylate salt (sodium propanoate) and an alcohol (methanol).

💡 Key Knowledge

  • Reagents: Aqueous sodium hydroxide ( NaOH(aq) ) and heat (reflux).
  • Acid vs Alkaline: Acid hydrolysis is reversible and produces a carboxylic acid + alcohol. Alkaline hydrolysis goes to completion and produces a carboxylate salt + alcohol because the salt reacts with the alkaline conditions.

🧠 Exam Technique

Split the ester molecule at the ester bond (-COO-):

  1. The acyl part ( CH₃CH₂CO- ) forms the carboxylate salt with Na⁺ .
  2. The alkyl part from the alcohol ( -OCH₃ ) gains an H from water/hydroxide processing to form the neutral alcohol ( CH₃OH ).

❌ Common Errors

Students often select option A because they confuse alkaline hydrolysis with acid hydrolysis. Remember that in an alkaline environment containing Na⁺ and OH⁻ ions, any carboxylic acid formed would immediately neutralize to create a carboxylate salt ( R-COO⁻Na⁺ ).

Mark Scheme Allocation: 1 mark available (AO1.2 - Demonstrating knowledge and understanding of organic reaction mechanisms and products). Correct option is B.

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), November 2021. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.