Laboratory Methods of Organic Chemistry - Sciencemadness Dot Org

OH
BKOMINATION OF PHENOL 243
HOBr
The substitution of the second and third bromine molecules proceeds
in the same way until the three favoured positions (o-, o-, and p-) are
occupied by bromine. If now a fourth molecule of bromine is allowed
to act on the tribromo-derivative, this molecule is attached at the
1 : 4-positions in fundamentally the same way as that assumed here :
OH
In this case, however, the elimination of HBr can no longer lead to
the production of a true benzene derivative. Actually the so-called
" tribromophenol bromide ", the final product of the above reaction, is
the ketobromide of a quinone and hence a derivative of dihydrobenzene.
The technical uses of phenol are important, particularly in the manufacture
of salicylic acid (Chap. VI. 4, p. 249), and in that of the valuable
synthetic resins of the " bakelite " type (condensation with formaldehyde).
Under mild conditions phenol may be caused to combine with
formaldehyde giving -p-hydroxybenzyl alcohol:
+ OCH,—
3H2OH
This alcohol, when warmed, loses water and polymerises.
The direct introduction of mercury into the benzene ring of the
phenols must also be mentioned here. It is sufficient to heat with
mercuric acetate (Balbiano, Pesci, Dimroth) in order to bring about this
reaction.