Alcohols Phenols And Ethers Ques 36
36. The ionization constant of phenol is higher than that of ethanol because :
[2000]
(a) Phenoxide ion is bulkier than ethoxide
(b) Phenoxide ion is stronger base than ethoxide
(c) Phenoxide ion is stabilized through delocalization
(d) Phenoxide ion is less stable than ethoxide
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Solution:
- (c) The acidic nature of phenol is due to the formation of stable phenoxide ion in solution
$ C_6 H_5 OH+H_2 O \rightarrow \underset{\text{ Phenoxide ion }}{C_6 H_5 O^{-}}+H_3 O^{+} $
The phenoxide ion is stable due to resonance.
The negative charge is delocalized in the benzene ring which is a stabilizing factor in the phenoxide ion and increase acidity of phenol, wheras no resonance is possible in alkoxide ions $(RO^{-})$derived from alcohol. The negative charge is localized on oxygen atom. Thus, alcohols are less acidic.
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