Patent GB-760200-A (GB)
Title: Purification of dihydric phenols
IPC: C07C39/08
Filed: 1954-12-02
Abstract: Resorcinol, hydroquinone or pyrocatechol are purified by azeotropic distillation with a chlorinated biphenyl containing 20-35 per cent of combined chlorine and crystallizing the dihydric phenol from the distillate.  The crude dihydric phenols may be obtained by acid catalysed decomposition of a diisopropylbenzene dihydroperoxide when any isopropyl phenol impurities distil with the azeotrope but remain in the mother liquor during crystallization of the dihydric phenol and may be removed therefrom by extraction with caustic alkali.  The chlorinated biphenyl may be a mixture of two or more isomers having a boiling range of 275 DEG  to 325 DEG  C. and may be obtained by the chlorination of biphenyl.  The distillation may be conducted at reduced, atmospheric or elevated pressure.  The chlorinated biphenyl mother liquors may be re-used in subsequent distillations with periodic purification by washing with alkali, and by treatment with decolourizing charcoal, and distillation.  In examples: (1) m-diisopropylbenzene dihydroperoxide is decomposed with sulphuric acid in acetone, the acid neutralized and low-boiling material distilled off, chlorinated biphenyl is added and the mixture distilled, resorcinol crystallizing from the distillate on cooling; (2) as in (1) above but the neutralization of the catalyst is omitted, giving a similar result; (3) a product obtained by acid-catalysed cleavage of a m-diisopropylbenzene oxidate is distilled with a chlorinated biphenyl, resorcinol crystallizing from the distillate and m-isopropyl phenol being extracted from the mother liquors with aqueous caustic soda; (4), (5), (6) and (7) illustrate the azeotropic distillation of commercial resorcinol, hydroquinone and pyrocatechol with chlorinated biphenyl, the purified dihydric phenol crystallizing from the distillate; (8) hydroquinone contaminated with p-isopropyl phenol and obtained by decomposition of a p-diisopropylbenzene oxidate is distilled with chlorinated biphenyl, hydroquinone crystallizing from the distillate, the mother-liquors of which are extracted with aqueous caustic soda which is then acidified to give p-isopropyl phenol.  U.S.A. Specification 1,912,628 is referred to.ALSO:Resorcenol, hydroquinone, or pyrocatechol are purified by azeotropic distillation with a chlorinated biphenyl containing 20-35 per cent of combined chlorine and crystallizing the dihydric phenol from the distillate.  The chlorinated biphenyl may be a mixture of two or more isomers having a boiling range of 275 DEG C. to 325 DEG C. and may be obtained by the chlorination of biphenyl.  The distillation may be conducted at reduced, atmospheric or elevated pressures.  The chlorinated biphenyl mother-liquors may be re-used in subsequent distillations with periodic purifications by washing with alkali, or by treatment with decolourizing charcoal, and distillation.  The crude dihydric phenols may be obtained by catalytic decomposition of diisopropyl-benzene dihydroperoxides (see Group IV (b)).  In an example, a chlorinated biphenyl containing 32 per cent chlorine is added to a crude m-diisopropylbenzene dihydroperoxide decomposition product and distilled, resorcinol crystallizing from the distillate on cooling. U.S.A. Specification 1,912,628 is referred to.