OCR A-Level Chemistry Synthesis and analytical techniques (02), June 2017: Question 7

1 mark · Medium difficulty · Multiple Choice

Identify which given molecular structure represents a secondary amine

Practise this question

Question

Multiple choice question 7 asking which molecule is a secondary amine, showing four chemical structures labeled A, B, C, and D. Structure A shows a ketone and secondary amine functional group, B shows an amide with an NH group, C shows a tertiary amide, and D shows a ketone with a tertiary amine group.
Question text

7 Which molecule is a secondary amine?

O NH N O

NH O O N

A B C D

Your answer

[1]

Mark scheme

Show the mark scheme The mark scheme indicates that the correct answer for question 7 is A.

7 A 1

How to answer it

Identifying Functional Groups: Secondary Amines

What this question tests

This question assesses your ability to recognise and distinguish between different organic functional groups—specifically amines and amides—and to correctly classify the degree of substitution (primary, secondary, or tertiary) of an amine group based on its structural formula.

Question 7

Identifying a Secondary Amine

✅ Correct Answer

A

Awarded 1 mark for selecting option A.

💡 Key Knowledge

  • Primary Amine (R-NH₂): Nitrogen is bonded to one alkyl/aryl group and two hydrogen atoms.
  • Secondary Amine (R₁-NH-R₂): Nitrogen is bonded to two alkyl/aryl groups and one hydrogen atom.
  • Tertiary Amine (R₁R₂R₃N): Nitrogen is bonded to three alkyl/aryl groups and zero hydrogen atoms.
  • Amides (R-CO-NH-R): Contain a carbonyl group ( C=O ) directly bonded to the nitrogen atom, which alters their chemical properties compared to amines.

🧠 Exam Technique

  • Scan the molecules systematically: eliminate structures containing a C=O (carbonyl) group attached to nitrogen, as these are amides, not amines (eliminates B and C).
  • Examine the remaining nitrogen-containing groups (A and D) and count how many carbon chains (alkyl groups) and hydrogen atoms are attached directly to the nitrogen atom.

❌ Common Errors

  • Confusing amides with amines: Options B and C feature a peptide/amide linkage ( O=C-NH/N ). Students often mistake the -NH- inside an amide group for a secondary amine.
  • Miscounting substitution: Option D features a nitrogen bonded to two methyl groups and an alkyl chain ( -N(CH₃)₂ ), making it a tertiary amine, not secondary. Option A correctly features an -NH- group linking a methyl group to the main carbon chain without a nearby carbonyl.

Topics

Module 6: Organic chemistry and analysis · 6.2 Nitrogen compounds, polymers and synthesis

Question and mark scheme from the OCR A-Level Chemistry examination, Synthesis and analytical techniques (02), June 2017. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.