Question

The ionisation constant of phenol is higher than that of ethanol because

• A. Phenoxide ion is bulkier than ethoxide
• B. Phenoxide ion is stronger base than ethoxide
• C. Phenoxide ion is stabilised through delocalisation
• D. Phenoxide ion is less stable than ethoxide

Answer 1

The correct option is C

Phenoxide ion is stabilised through delocalisation

Phenoxide ion is stable due to resonance. The -ve charge is delocalised in the benzene ring which is a stabilising factor in the phenoxide ion and because of this ionisation constant of phenol is higher whereas no resonance is possible in alkoxide ions derived from alcohol. The -ve charge is localised on oxygen atom in case of alcohol