Q6(j). ν(C=C) of methylidenecycloalkanes and ring size
Arrange the following olefins in the correct order of IR stretching frequency of C=C and explain your answer. [structures of the methylidenecycloalkanes A–D given in the paper]
Answer in brief
ν(C=C): C > D > A > B, about 1780, 1678, 1657 and 1651 cm⁻¹; the smaller the ring, the higher the frequency of the exocyclic C=C.
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CoversIR spectroscopyC=C stretching frequencyexocyclic double bondring strainmethylenecyclopropane
All parts of Question 6
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- 6(g) [1,5]-Carbon shift and Cope rearrangement4 marks
- 6(h) Four C₁₀H₁₄ isomers: the one marked by a McLafferty peak4 marks
- 6(i) C₃H₇NO with two N–methyl singlets: N,N-dimethylformamide4 marks
- 6(j) ν(C=C) of methylidenecycloalkanes and ring size4 marks