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The transition state for -hydride elimination in alkyl groups on the Pt(111) surface has been probed by studying the effects of fluorine substitution on the barriers to -hydride elimination, %@mt;sys@%%@ital@%E%@rsf@%%@sx@%H%@be@%‡%@sxx@%%@mx@%. Four different fluoroalkyl groups have been formed on the Pt(111) surface by dissociative adsorption of four fluoroalkyl iodides:  RCH2CH2−I (R CF3, CF3CH2, and CF3CF2) and (CF3)2CHCH2−I. In the absence of preadsorbed hydrogen, fluoroalkyl groups on the Pt(111) surface dehydrogenate via -hydride elimination to form unsaturated fluorocarbons and deposit hydrogen atoms onto the surface. Those hydrogen atoms then hydrogenate the remaining fluoroalkyl groups to produce fluoroalkanes that desorb rapidly from the surface. The kinetics of hydrogenation and fluoroalkane desorption are rate limited by the -hydride elimination step and thus serve as measures of the kinetics of -hydride elimination. The field effects of the fluorinated substituents increase the barriers to -hydride elimination with a reaction constant of F 19 ± 2 kJ/mol. The interpretation of this effect is that the -carbon atom in the transition state is cationic, RC···H‡, with respect to the reactant. The field effect of the fluorinated substituent energetically destabilizes the electron deficient -carbon atom in the transition state. This is consistent with observations made on the Cu(111) surface; however, the substituent effect is significantly smaller on the Pt(111) surface. On the Pt(111) surface, the transition state for -hydride elimination is less polarized with respect to the initial state alkyl group than on the Cu(111) surface. [ABSTRACT FROM AUTHOR]

Abstract: 4-Benzylideneamino-1,2,4-triazine-3,5(2H,4H)-diones (2–5), 6-styryl-1,2,4-triazine-3,5(2H,4H)-dione (6), and 6-styryl-2,3-dihydro-3-thioxo-1,2,4-triazin-5(4H)-one (7) were synthesized and pyrolyzed in the gas phase. The kinetic effect of changing the substituent on the triazine ring from hydrogen to methyl, phenyl, and styryl was measured. Analyses of the pyrolyzates of 2–5 showed the elimination products to be benzonitrile and the triazine fragment, while the pyrolyzates of 6 and 7 reveal the formation of cis- and trans-cinnamonitriles. Theoretical study of the pyrolysis reactions of 2–5 using an ab initio SCF method was investigated. [Copyright &y& Elsevier]

Abstract: Nitrogen and hydrogen isotope effects for the reaction of N-tert-butyl-P-phenylphosphonamidothioic acid 1 with alcohols (methanol, butanol, iso-propanol, tert-butanol) were measured in dichloromethane at 30 °C. The observed nitrogen isotope effect k 14/k 15 is only slightly sensitive to a steric hindrance of the alcohol [1.0070±0.0002 (MeOH), 1.0074±0.0004 (BuOH), 1.0062±0.0004 (Pr i OH), 1.0087±0.0007 (Bu t OH)]. The pre-equilibrium step, with proton transfer from oxygen to nitrogen was proved by the inverse hydrogen effect k ROH/k ROD[0.778±0.052 (MeOH), 0.863±0.063 (BuOH), 0.883±0.080 (Pr i OH), 0.746±0.084 (Bu t OH)]. The experimental values are consistent with theoretical results of semiempirical calculations on PM3 level for an elimination–addition mechanism and metathiophosphonate PhPSO intermediacy. For the reaction with methanol the addition–elimination mechanism is also possible. [Copyright &y& Elsevier]

The radical reaction of tributyltin hydride with o-iodo-N- methylanilides derived from α-azido acids provides an excellent access to α-(aminocarbonyl)iminyl radicals through 1,5-hydrogen transfer reaction of initially formed aryl radicals followed by β-elimination of dinitrogen from ensuing α-azido-α-(aminocarbonyl)alkyl radicals. The outcoming iminyls display a peculiar tendency to form corresponding nitriles by β-elimination of aminocarbonyl radicals. [ABSTRACT FROM AUTHOR]