Reactions of H<sub>3</sub>O<sup>+</sup> and H<sub>2</sub>O<sup>+</sup> with Several Fully Halogenated Bromomethanes
作者:R. D. Thomas、R. A. Kennedy、C. A. Mayhew、P. Watts
DOI:10.1021/jp9719624
日期:1997.11.1
The bimolecular rate coefficients and ion products for the reactions of H3O+ and H2O+ with the bromine-containing molecules CF3Br, CF2Br2, CF2BrCl, CFBr3, CFBr2Cl, and CBrCl3 at 300 K are reported. With the exception of the reactions of H3O+ with CF3Br and CF2BrCl, the rate coefficients are near the collisional values (k approximate to 10(-9) cm(3) molecule(-1) s(-1)). The most efficient exit pathway for the majority of the H3O+ reactions is the formation of a trihalomethyl cation, together with water and a hydrogen halide as the neutral products. In each case, more than one trihalomethyl cation can be formed. The branching ratios are largest for the products resulting from the breaking of a C-F bond. This is attributed to the high bond strength of HF relative to HCl and HBr. Similarly for CBrCl3, the major product cation is CCl2Br+. The H2O+ reactions are found to proceed predominantly via charge transfer. For the reaction of H2O+ with CF3Br there is clear evidence for intimate reaction pathways in which bonds are broken and formed.
Chemical ionization mass spectrometry of halomethanes with tetramethylsilane as reagent gas
作者:Oleg S. Chizhov、Valentin I. Kadentsev、Andrei A. Stomakhin
DOI:10.1002/oms.1210270610
日期:1992.6
AbstractChemical ionization mass spectra of halomethanes measured using tetramethylsilane as reagent gas exhibit three major peaks corresponding to [M + SiMe3]+, [M − X]+ and (MeSi)2X+ ions (X = Cl, Br or I). Dihalomethanes CH2X2 form the most stable silylated molecular ions, whereas in the mass spectra of tetrahalomethanes (CX4) these ions have not been detected and the ions CX3+ are the most abundant. Production of bistrimethylsilyl‐halonium ions is the most pronounced process for haloforms (CHX3).