Formaldehyde → 2,4'-Dihydroxydiphenylmethane

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Several methods are known in the art for the production of dihydroxydiphenylmethanes. Japanese Patent Jpn. Kokai Tokkyo Koho JP 0687775 (CA 121:57131) discloses a method for the condensation of phenol with aqueous formaldehyde using phosphotungstic acid which consists of 10:43:47 ratio of 2,2′-, 2,4′- and 4,4′-dihydroxydiphenylmethane isomers. EP 331, 172: CA 112:7160 discloses a method for reacting phenol with formaldehyde in the presence of an activated clay at 80° C. for 2 hours to give 38.8% of 4,4′-, 15.8% of 2,2′-, and 38.4% of 2,4′-dihydroxydiphenylmethane and 7.0% oligomer JP 63, 238, 632: CA 116: 75045 discloses a method for reacting phenol with formaldehyde in the presence of activated clay catalyst to give 2,2′-, 2,4′-, and 4,4′dihydroxydiphenylmethane in the ratio of 17.1: 41.4:44.5.

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