Compound(s) that show(s) an intense peak at \( m/z = 120 \) in the EI mass spectrum is/are:
Show Hint
The Correct Option is A, B, D
Solution and Explanation
The intense peak at m/z = 120 in EI (Electron Impact) mass spectrometry often corresponds to the tropylium ion (C7H7+), a very stable aromatic cation. This ion is formed by the fragmentation of alkyl-substituted benzyl systems.
- (A) The compound is phenylbutanone. On EI ionization, it can lose the carbonyl side chain and rearrange to form the stable tropylium ion (m/z = 120). CORRECT
- (B) The structure is similar, with an isopropyl substitution. Fragmentation also allows formation of the tropylium ion. CORRECT
- (C) This is a salicylic acid derivative. No alkyl chain or benzylic system is available to form the tropylium ion. WRONG
- (D) This is methyl salicylate. On fragmentation, the ester moiety can allow tropylium ion formation via rearrangement. CORRECT
✅ Final Answer: Compounds (A), (B), and (D) show a peak at m/z = 120.
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