A Levels Chemistry (9701)•9701/12/M/J/22
Explanation
m/z 43 fragments from alcohol ionizations Steps:
- Ethanol (CH3CH2OH) undergoes rearrangement in EI-MS to form C2H3O+ (mass 43).
- Propan-1-ol (CH3CH2CH2OH) fragments via loss of OH• to yield CH3CH2CH2+ (C3H7+, mass 43).
- Propan-2-ol ((CH3)2CHOH) fragments via alpha-cleavage to yield (CH3)2CH+ (C3H7+, mass 43).
- All three alcohols show this peak due to common EI-MS pathways for small primary/secondary alcohols.
Why D is correct:
- Each compound produces a distinct ion of mass 43 (C2H3O+ for ethanol, C3H7+ for propanols) per standard mass spectrometry fragmentation rules.
Why the others are wrong:
- A excludes propanols, ignoring their C3H7+ ions.
- B excludes propan-2-ol, overlooking its isopropyl cation.
- C excludes ethanol, missing its C2H3O+ rearrangement product.
Final answer: D
Topic: Analytical techniques
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