PHOTOOXIDATION OF (+/-)-2-BUTANOL TO 2-BUTANONE USING POLYOXOMOLYBDATE(VI) CATALYSTS - A CLEAN AND HIGH YIELD ROUTE

摘要

No colour change occurred when a colourless, aqueous solution of the beta-octamolybdate(VI) salt [Et(3)NH](4)[Mo8O26] (1) was irradiated with UV light (lambda = 254 nm). Similarly, an irradiated solution of 1 in a water:(+/-)-2-butanol mixture also remained colourless and no gaseous hydrogen evolved. In contrast, aqueous solutions of the alkali and alkaline earth metal containing salts [Et(3)NH](3)[NaMo8O26] (2) and [Et(3)NH](2)[Mg (H2O)(6)MO(8)O(26)]. 2H(2)O (3) both turned blue (lambda(max) = 725 nm) when irradiated with UV light. Irradiated solutions of 2 and 3 in a water: (+)-2-butanol mixture also turned blue, and 2-butanone along with hydrogen gas were produced in almost quantitative yield over a 24 h reaction period. Likewise, an aqueous solution containing 1 and excess of an alkali or alkaline earth metal chloride salt (e.g. NaCl, KCl, MgCl2, CaCl2 or SrCl2) also catalysed the photooxidation of (+/-)-2-butanol. Product yields were again greater than or equal to 90%. [References: 15]