24.19The three parts of this problem make up the series of steps by which o-bromophenol is prepared.(a)Because direct bromination of phenol yields both o-bromophenol andp-bromophenol, it isessential that the para position be blocked prior to the bromination step. In practice, what isdone is to disulfonate phenol, which blocks the para and one of the ortho positions.(b)Bromination then can be accomplished cleanly at the open position ortho to the hydroxylgroup.(c)After bromination the sulfonic acid groups are removed by acid-catalyzed hydrolysis.24.20
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