Effect of water on the radiolysis of liquid acetone

Abstract

Liquid acetone is quickly and efficiently dried with 4 a molecular sieve. Small concentrations (up to 0.4% v/v) of water greatly affect the radiolysis of liquid acetone ; the yields of hydrogen, methane, and hexane-2.5-dione are increased and the yields of ethyl methyl ketone and 4-hydroxy-4-methylpentan-2-one are decreased. These effects are interpreted in terms of ionic reactions, for which there exists evidence from ion-molecule studies and from spectroscopic work with low temperature glasses. SOME product yields from the radiolysis of liquid acetone are markedly affected by the drying procedure used; hydrogen and methane yields are less when acetone is dried with phosphorus pentoxide than with undried acetone,l and the yields of acetic acid, acetaldehyde, and and hexane-2,5-dione are less when phosphorus pent oxide rather than potassium carbonate is used as a desiccant.2 Drying with phosphorus pentoxide causes irreversible eff ects,3 which possibly arise from chemical dehydration. We have examined several desiccants and investigated the effect of addition of small amounts of water upon the radiolysis of dried acetone. Increases in the hydrogen yield from the radiolysis of liquid 1,4-dioxan upon addition of water have been o b ~e r v e d . ~. ~ EXPERIMENTAL Calcium chloride, calcium sulphate, potassium carbonate, and 4 A and 5 A molecular sieves were tried as drying agents. Calcium chloride and potassium carbonate were inefficient and slow (ca. 0.05% vjv water after contact for 1 day) and molecular sieves were most efficient and rapid (0.003% v/to water after contact for 1 hr.). There was evidence of chemical breakdown of acetone only after 7 days drying with molecular sieves ; other desiccants showed this in much shorter times. Drying was generally performed by contact, with occasional shaking, with 4 A molecular sieve pellets for 1 hr. W7ater in acetone was determined by g.1.c. on a column (1 m.) of Carbowax 1500 on Teflon G with a hot wire detector.