66186-10-5Relevant academic research and scientific papers
Gas-phase chemistry of the silaformyl anion, HSiO-
Gronert, Scott,O'Hair, Richard A. J.,Prodnuk, Stephen,Sülzle, Detlev,Damrauer, Robert,DePuy, Charles H.
, p. 997 - 1003 (1990)
The silaformyl anion, HSiO-, has been prepared by collisionally induced dissociation (CID) of H3SiO in a tandem flowing afterglow selected ion flow tube (FA-SIFT). The chemistry of the silaformyl anion has been studied in detail. Reactions with CO2, COS, CS2, SO2, O2, acetic acid, nitromethane, and hexafluorobenzene reveal a rich chemistry. For example, the silaformyl anion reacts with CO2 by both an oxidative pathway giving HSiO2- and CO and a reductive path giving SiO and HCO2-. Typically, the silaformyl anion, which could have several sites of reactivity, behaves both as an oxygen nucleophile and as a hydride donor. Detailed mechanistic studies have been carried out on many of these reactions with isotopically labeled H29SiO- and HSi18O-. In addition to its reaction chemistry, the heat of formation of the silaformyl anion, its basicity, and the heat of formation of its parent compound have been estimated. Ab initio computations on the silaformyl anion have been carried out and demonstrate that HSiO- is more than 40 kcal/mol more stable than HOSi-.
Comparison of ΔG°Acid (gas phase) and kinetic acidities measured in methanolic sodium methoxide
Koch, Heinz F.,Biffinger, Justin C.,Mishima, Masaaki,Mustanir,Lodder, Gerrit
, p. 614 - 617 (2007/10/03)
Hydron exchange rates, kexc (M-1s-1), using methanolic sodium methoxide were compared with ΔG°Acid, (kcal mol-1) (gas phase) for 9-phenylfluorene, C6H5CH(CF3)2, m-CF3C6H4CH(CF3)2, p-CF3C6H4CHClCF3, m-CF3C6H4CHClCF3, 3,5-(CF3)2C6H3CHClCF3, fluorene and C6F5H. There is a good linear correlation for p-CF3C6H2CHClCF3, m-CF3C6H4CHClCF3 and 3,5-(CF3)2C6H3CHClCF3, with the others falling off the line. The fluorinated benzyl compounds and pentafluorobenzene have near-unity isotope effects and therefore differ from the fluorenyl compounds. Although the acidity and the exchange rates for three of the compounds [9-phenylfluorene, C6H5CH(CF3)2 and p-CF3C6H4CHClCF3] are similar, the important proton-transfer step to form a hydrogen-bonded carbanion intermediate and the subsequent breaking of that weak bond to form a free carbanion in methanol differ significantly for the fluoernyl compound compared with the two fluorinated benzylic compounds.
Proton transfer between carbon acids and methoxide: Studies in methanol, the gas phase and by Ab initio MO calculations
Koch, Heinz F.,Mishima, Masaaki,Zuilhof, Ban
, p. 567 - 572 (2007/10/03)
A detailed mechanism that features hydrogen-bonded carbanions as well as free carbanions is presented for hydrogen transfer between carbon acids and methoxide ion in methanol. This is refined for several compounds by measuring their gas phase acidities, ΔGAcid0 kcal/mol: C6H5CH(CF3)2 [335.3]; p-C6H4CHClCF3 [337.4]; 9-phenylfluorene [335.6]; C6F5H [349.2]. Ab inilio molecular orbital calculations are reported to evaluate the stability of possible intermediates along the reaction pathway from 2-hydro-2-phenyl-perfluoropropane and methoxide ion to the carbanion and methanol. The intermediate, {C6H5C(CF3)2} -·HOCH3, is 6.8 kcal/mol more stable than the separated species, {C6H5C(CF3)2}- and CH3OH, and 43.2 kcal/rnol more stable than C6H5CH(CF3)2 and -OCH3. WILEY-VCH Verlag GmbH, 1998.
Gas-phase ion chemistry of HP2-, FP2-, and HP2+
O'Hair, Richard A. J.,Krempp, Michèle,Damrauer, Robert,DePuy, Charles H.
, p. 2092 - 2096 (2008/10/08)
The gas-phase ion-molecule chemistry of the mass-selected ions HP2-, FP2-, and HP2+ has been studied in a tandem flowing afterglow selected-ion flow tube (FA-SIFT). Both HP2- and HP2+ are formed by direct electron impact on phosphine, followed by subsequent ion-phosphine reactions in the first flow tube. The related ion, FP2-, is formed via an ion-molecule reaction between HP2- and hexafluorobenzene. We have observed a number of reactions of HP2-, including hydride transfer and proton abstraction, as well as fluoride transfer and proton abstraction for FP2-. Using bracketing techniques, the gas-phase proton affinity of P2 has been determined as 162 ± 3 kcal mol-1, in good agreement with Nguyen and Fitzpatrick's theoretically predicted value of 158 ± 3 kcal mol-1. The heats of formation of HP2-, HP2+, HPPH, FP2-, and FPPH have been estimated from the experimentally determined hydride, proton and fluoride affinities of P2 and from the gas-phase acidities of HPPH and FPPH.
