Process for the production of 2,2'-dihydroxy-biphenyls

A process for the production of a 2,2'-dihydroxybiphenyl of the formula I ##STR5## wherein each of R.sub.1 and R.sub.2 independently is hydrogen, C.sub.1 -C.sub.18 alkyl, C.sub.2 -C.sub.6 alkenyl, or C.sub.5 -C.sub.7 cycloalkyl, phenyl or C.sub.7 -C.sub.9 phenylalkyl, each of which is unsubstituted or substituted by one to three C.sub.1 -C.sub.4 alkyl radicals, or R.sub.1 and R.sub.3 together are a butadi-1,3-enyl-1,4-ene radical which is bonded to the benzene ring in the 3,4 and 3', 4'-positions, and R.sub.2 is also a --(CH.sub.2).sub.n COOR.sub.4 group, wherein R.sub.4 is C.sub.1 -C.sub.18 alkyl and n is 0, 1 or 2, and R.sub.3 is hydrogen or C.sub.1 -C.sub.18 alkyl, with the proviso that when R.sub.1 is hydrogen, R.sub.2 and R.sub.3 are a 1,1,3,3-tetramethylpropylene radical which is bonded to the benzene ring in the 4,5- and 4',5'-positions, which process comprises oxidatively coupling, at elevated temperatures, a phenol of the formula II ##STR6## wherein R.sub.1, R.sub.2 and R.sub.3 are as defined above, with hydrogen peroxide in the presence of a strong inorganic base.