Reactions of gas-phase salts: Substitutions and eliminations in complexes containing a dianion and a tetraalklylammonium cation

[GRAPHICS] Electrospray ionization has been used to generate gas-phase complexes of a dianion (4 carboxy-4'-sulfodiphenylacetylene) with a series of tetraalkylam monium cations. The salt complexes are stable within a quadrupole ion trap but readily react during collision activated dissociation to give substitut ion and elimination products (alkylation or protonation of the carboxylate with the loss of a trialkylamine). Ab initio calculations at the MP2/6-31 G(d,p)/MP2/6-31 +G(d) level are presented for the corresponding reactions o f a model system, acetate + ethyltrimethylammonium.