Q8(c)(ii). Two carbonyl bands of chloroacetone
Acetone exhibits only one carbonyl stretching frequency in its IR spectrum whereas chloroacetone exhibits two, at 1725 and 1745 cm⁻¹. Explain why.
Answer in brief
Chloroacetone exists as two rotational isomers: with Cl cis to C=O the field effect raises ν(C=O) to 1745 cm⁻¹, while the gauche conformer absorbs at 1725 cm⁻¹.
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CoversIR spectroscopyfield effectrotational isomerschloroacetonecarbonyl stretching frequency
All parts of Question 8
- 8(a)(i) Products X and Y in four reagent problems15 marks
- 8(a)(ii) 2-Methylbut-1-ene with diborane5 marks
- 8(b)(i) C₉H₁₈O with a single ¹H NMR line10 marks
- 8(b)(ii) Two UV bands of acetone5 marks
- 8(c)(i) ¹H NMR spectrum of methyl propenoate10 marks
- 8(c)(ii) Two carbonyl bands of chloroacetone5 marks