In phenol, the carbon–oxygen bond length is shorter (136 pm) than in methanol due to partial double bond character resulting from the conjugation of the unshared electron pair of oxygen with the aromatic ring and the sp² hybridization of the carbon to which oxygen is attached.
Why is the carbon–oxygen bond length in phenol slightly less than that in methanol, and what contributes to this difference?
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The carbon–oxygen (C–O) bond length in phenol is slightly less than that in methanol due to resonance effects. Phenol exhibits resonance structures, leading to electron delocalization within the aromatic ring. This resonance contributes to partial double-bond character in the C–O bond, shortening the bond length. In contrast, methanol lacks resonance stabilization, resulting in a more straightforward single bond. The delocalization of electrons in phenol makes the C–O bond stronger and shorter compared to the single bond in methanol, where electrons are localized between the carbon and oxygen atoms, causing a longer bond length.