Chemical reactions on clusters. Part 6.—Reactions of simple ketones in association with argon and carbon dioxide clusters

Abstract

Ion clusters of the type Ar_n·CH₃COC₂H⁺₅, Ar_n·CH₃COC₃H⁺₇, (CO₂)_n·CH₃COC₂H⁺₅ and (CO₂)_n·CH₃COC₃H⁺₇ for n= 1 to 21 have been formed by electron impact following the adiabatic expansion of an inert gas–ketone mixture. In each case the ketone was observed to undergo unimolecular decomposition to give Ar_n·R_LCO⁺, Ar_n·R_sCO⁺, (CO₂)_n·R_LCO⁺ and (CO₂)_n·R_sCO⁺, where R_L and R_s represent the larger and smaller aliphatic grouping on either side of the carbonyl group, respectively. Other products, which are present in the mass spectrum of the isolated ion, do not appear when the ketones are clustered with argon and carbon dioxide. These observations are discussed in terms of an integral cluster structure where the oxygen atom is retained in all the reaction products and steric interactions prevent it from participating in any rearrangement processes.