- The Torsional Barrier around the Phenyl-C+ Bond in Phenylcarbenium Ions
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The barrier to rotation around the phenyl-carbenium carbon bond in a series of carbenium ions R1R2C+Ph (with R1 and/or R2=H, CH3, cyclopropyl, and C6H4X) has been measured by complete line-shape analysis of the n.m.r. spectra or by the spin saturation transfer method. ΔG(excit.) Values range from 36 to 78 kJ mol-1.The results are discussed in terms of steric and electronic contributions and the relationship of the 13C chemical shift of the carbenium centre with the ?C+ values of the para-substituent is analysed.
- Jost, Roland,Sommer, Jean
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- Properties and Reactions of Trimethyl Phosphite, Trimethyl Phosphate, Triethyl Phosphate, and Trimethyl Phosphorothionate by Ion Cyclotron Resonance Spectroscopy
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The gas-phase ion-molecule reactions occurring in trimethyl phosphite, trimethyl phosphate, triethyl phosphate, and trimethyl phosphorothionate have been investigated by ion cyclotron resonance spectroscopy.Protonated parent ions, tetracoordinated phosphonium ions, and cluster ions are the reaction products observed.The proton affinities of these compounds have been determined to be 222.9, 214.2, 218.7, and 216.6 kcal/mol, respectively (relative to PA(NH3) = 207.0 kcal/mol).Homolytic bond dissociation energies of the protonated species are calculated using adiabatic ionization potentials determined by photoelectron spectroscopy.The trends in these quantities are discussed.A reasonable value for the correlated homolytic bond dissociation energy of trimethyl phosphite indicates that the first ionization potential of this molecule should be assigned to the phosphorus lone pair.The application of chemical ionization mass spectrometry to the analysis of phosphorus esters is briefly discussed.
- Hodges, Ronald V.,McDonnell, T. J.,Beauchamp, J. L.
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p. 1327 - 1332
(2007/10/02)
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