Arsenical creosote. VI. Importance of the vicinal hydroxyls in the reaction of phenols with arsenic trioxide

Only those compounds with vicinal hydroxyls on the benzene ring reacted extensively with As₂O₃ when heated at 130–16° in high-temperature coke-oven creosote. About two moles of 1,2-dihydroxybenzene, 1,2-dihydroxy-3-methylbenzene and 1,2-dihydroxy-4-methylbenzene reacted with one mole of As₂O₃; for 1,2,3-trihydroxybenzene and 3,4-dihydroxybenzoic acid the ratio was about 2·7 and for 3,4,5-trihydroxybenzoic acid it was still higher. Similar reactions occurred in heavy petroleum, raw linseed, lubricant and paraffin oils. Arsenic derivatives have been synthesised either by gentle fusion of mixtures of the above compounds with As₂O₃, or by heating the reactants for 75 min in paraffin oil. The products, recrystallised from toluene, petroleum ether or toluene–ethanol are white, odourless, non-volatile and stable at temperatures of 150–200°.