THIOACYLIUM IONS. GAS-PHASE ION-MOLECULE REACTIONS OF THIOIC AND DITHIOIC ACID DERIVATIVES.

Article abstract of DOI:10.1021/ja00361a026

Thioacylium ions CH//3CS** plus and C//2H//5CS** plus can be generated in the gas phase from acylium ions CH//3CO** plus and C//2H//5CO** plus and ethanethioic and propanethioic acids by using ion cyclotron resonance techniques. Similarly, CH//3CS** plus is formed in the ion chemistry of acetyl sulfide. Evidence to support the thioacylium structure for these ions was obtained from the nature of their reactions (proton transfer and thioacylation) and from the fact that they behave indistinguishably from thioacylium ions generated by EI cleavage of O-methyl ethanethioate and methyl ethanedithioate, CH//3C(S)XCH//3,X equals O,S. The heat of formation of CH//3CS** plus is estimated to be 210 kcal mol** minus **1. Mechanism studies with isotopically labeled reactants show that association of acylium ions with neutral S-acyl compounds leads to thioacylium ions by attack of RCO** plus at sulfur and to acylium ions (R prime CO** plus ) by attack at carbonyl oxygen.