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Phenol when reacts with bromine in presence of cs2 gives only para - bromo phenol but aniline gives tribromoaniline in same conditions,why?
Phenol when reacts with bromine in presence of CS2 gives only para - bromo phenol but aniline gives tribromoaniline in same conditions,Why?
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Priyanshu kumar Best Answer
Actually, water is a polar substance and so in bromine water, the phenol gives a strongly stable phenoxide ion. This ion has negative charge on oxygen and that transfers electrons to the benzene ring and that becomes much activated that substitution reaction occurs at three positions and tri-substituted product is obtained. But, CS2 is less polar solvent so the solvent effect is minimum and the formation of phenoxide ion is not much stable so the activation of ring also does not occur and thus only monosubstituted product is obtained. In case of aniline,as NH2 group has more electron donation effect than OH group i.e more activation power...so it give tribromo substitution products. For monobromination product we first decrease the electron donation power by acetylation so that acetanilide is formed which has less activation power than aniline..Then bromination occur leads to monobromination product.
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Achyut ranjan gogoi
aniline is more activating than phenol that's the only reason.