Alcohols and phenols both
are acidic in nature because they Liberate H2 with active metals. But alcohols
are weaker acids than phenols because,
(i) Alcohols fail
to turn blue litmus red:
(ii) Alcohols fail to
neutralize alkalies whereas phenols do so:
(1) Both phenol and
phenoxide ions exhibit resonance, whereas alcohols and alkoxide ion do not.
(2) Due to resonance, positive charge 's developed over "O" of phenol this weakens O-H bond and facilitates release of a proton. On the other hand due to electron donating nature of alkyl group -O-H bond is strengthened. Therefore it hinders the release of proton.
(2) Due to resonance, positive charge 's developed over "O" of phenol this weakens O-H bond and facilitates release of a proton. On the other hand due to electron donating nature of alkyl group -O-H bond is strengthened. Therefore it hinders the release of proton.
(3) The phenoxide ion
is more stable than phenol, due to greater dispersal of negative charge,
therefore. Equilibrium get shifted to forward direction. whereas alkoxide ion
is less stable than alcohols due to intensification of negative charge, so
equilibrium get shifted towards backward direction. Hence phenols are more
acidic than alcohols.
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