The Examiner's Assessment Bank
Structure 3.2 Exam Practice
Section A: High-Difficulty MCQs
1. What is the IUPAC name for ?
A. 1,1-dimethylpropan-2-ol
B. 3-methylbutan-2-ol (Correct)
C. 2-methylbutan-3-ol
D. Pentan-3-ol
2. Which molecule exhibits optical isomerism?
A. 1-chlorobutane
B. 2-chlorobutane (Correct)
C. 1-chloropropane
D. 2-chloropropane
3. What is the IHD of Aspirin ()?
A. 4
B. 5 (Correct)
C. 6
D. 7
Section B: Structured Data-Response
Q1: Isomerism & Properties [5 marks]
Consider the isomers of .
- Draw the structure of a tertiary alcohol isomer. [1]
- Compare the boiling point of this alcohol with its functional group isomer, ethoxyethane. Explain. [3]
- Identify which isomer of is optically active. [1]
Examiner's Markscheme
1. Structure of 2-methylpropan-2-ol.
2. The Alcohol has a higher boiling point. [1] Reason: Alcohols contain Hydrogen Bonding (strongest IMF). [1] Ethers only have Dipole-Dipole forces. [1]
3. Butan-2-ol. Asterisk on C2 (*).
Q2: Structural Elucidation (The Triangulation) [6 marks]
An unknown Compound X () presents the following data:
- IR: Strong, sharp peak at 1740 cm⁻¹ and no broad absorption above 3000 cm⁻¹.
- 1H NMR:
- Signal A: 1.3 ppm, Triplet, Integration 3H
- Signal B: 2.0 ppm, Singlet, Integration 3H
- Signal C: 4.1 ppm, Quartet, Integration 2H
Deduce the structure of Compound X. Justify using all data.
Examiner's Markscheme
- IHD: 1 (Consistent with C=O).
- IR: Peak at 1740 (C=O) + Absence of O-H = Ester. [1]
- NMR: Triplet (3H) + Quartet (2H) = Ethyl group. [1]
- Singlet (3H) indicates Isolated methyl next to C=O. [1]
- Signal C (4.1 ppm) confirms CH₂ is next to O (Ester link). [1]
- Structure: Ethyl Ethanoate (). [2]