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Question 18.36: Explain why the carbonyl stretching absorption of cyclohexan......

Explain why the carbonyl stretching absorption of cyclohexanones are shifted approximately 20 cm^{−1}  to higher wavenumber when a bromine atom is substituted in the equatorial position at the α carbon atom.

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The bromine atom withdraws electrons from the carbonyl carbon by an inductive effect. This increases the polarity of the carbonyl bond and, therefore, increases the energy required to stretch the carbonyl bond.

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