Thermochemical determinations by the kinetic method with direct entropy corrections and gas -phase ion /molecule reactions studied by tandem mass spectrometry.

摘要

Tandem mass spectrometry has been applied in probing the ion/molecule reactivity of some elusive species. Dicoordinated aminoborinium cation was found to undergo a gas-phase transacetalization reaction, i.e., the Eberlin reaction, with 1,3-dioxalanes and highly efficient gas-phase synthesis of an ionic B, N, and O-containing heterocyclic product (3,3-dimethyl-[1,3,2]oxazaborolidin-3-ium) is achieved. Taking advantage of the amphiphilic character of the phenylsulfenium cation, its gas-phase transacetalization reaction led to a ring contraction product. A related reaction between phosphonium ions and 1,4-dioxane was discovered. This reaction is very selective toward phosphonium cations, thus it has the potential to be applied to selective detection of chemical warfare agents in mixtures without preseparation. Besides direct addition at boron, the dicoordinated borinium cation can also under a bimolecular nucleophilic substitution (S N2) reaction with dimethylformalaldehyde (DMF). An interesting adduct was observed between nitrobenzene radical anion and neutral glycine. CID and ab initio calculation results suggest that two distinct forms of glycine exist in the complex, i.e., non-polar and zwitterionic.;The kinetic method has been increasingly applied in thermochemical determinations and gas-phase chiral analysis. A modified version of the kinetic method which explicitly considers the entropy contributions for reference compounds having dissimilar structures is described. This extends the kinetic method and allows it to be applied to cases where neither the assumption of zero protonation entropy difference of the standard kinetic method nor the pre-requirement of constant protonation entropy difference of the extended version of the method is satisfied.