Positive ion chemistry of fluoromethylsilanes, (CH/sub 3/)/sub n/SiF/sub 4-n/(n = 1-3), by ion cyclotron resonance spectroscopy. Fluorine and methyl substituent effects on the relative stabilities of siliconium ions, R/sup +/, and disilylfluoronium ions, RR'F/sup +/, in the gas phase

Journal Article · Wed Sep 15 00:00:00 EDT 1976 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00435a008· OSTI ID:7334397

Murphy, M K; Beauchamp, J L

The gas phase ion chemistry of the fluoromethylsilanes (CH/sub 3/)/sub n/SiF/sub 4-n/ (n = 1 - 3) has been investigated using the techniques of ion cyclotron resonance spectroscopy. Reaction pathways and rate constants have been determined for parent and major fragment ions by examination of ion abundances as a function of neutral pressure and of ion trapping time. Fluoride transfer reactions are a dominant feature of the observed ion chemistry and provide information relating to siliconium ion stabilities. Fluoride affinities of siliconium ions (D(R/sup +/-F/sup -/), heterolytic bond dissociation energies) indicate the order of decreasing relative stability of the fluoromethylsiliconium ions to be (CH/sub 3/)/sub 3/Si/sup +/ > (CH/sub 3/)/sub 2/SiF/sup +/ > CH/sub 3/SiF/sub 2//sup +/ > SiF/sub 3//sup +/. A second important feature of the observed ion chemistry concerns the formation and reactions of the fluorine and methyl substituted disilylfluoronium ions, RR'F/sup +/. Clustering reactions forming these species from R/sup +/ and R'F are shown to occur bimolecularly at low pressure, while collisional stabilization enhances the cluster formation rate at higher pressures. Subsequent displacement reactions indicate that the binding energies of the fluoromethylsiliconium ions to the fluoromethylsilanes decrease with increasing fluorine substitution in the neutral and in the siliconium ion moiety.

• Research Organization: California Inst. of Tech., Pasadena
• OSTI ID: 7334397
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 98:19; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400104 -- Spectral Procedures-- (-1987)
400201* -- Chemical & Physicochemical Properties
400301 -- Organic Chemistry-- Chemical & Physicochemical Properties-- (-1987)
BINDING ENERGY
CATIONS
CHARGED PARTICLES
CHEMICAL PROPERTIES
CHEMICAL REACTION KINETICS
ENERGY
GAS ANALYSIS
HYDRIDES
HYDROGEN COMPOUNDS
ION CYCLOTRON RESONANCE SPECTROSCOPY
ION PAIRS
ION SPECTROSCOPY
IONS
KINETICS
ORGANIC COMPOUNDS
ORGANIC FLUORINE COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
PRESSURE DEPENDENCE
REACTION KINETICS
SILANES
SILICON COMPOUNDS
SPECTROSCOPY
STABILITY
TRAPPING