Search Results - (Author, Cooperation:J. M. Pickard)

2014-10-03

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Animals ; Anorexia/complications/microbiology ; Bacteria/genetics/metabolism/pathogenicity ; Citrobacter rodentium/immunology ; Dendritic Cells/immunology/metabolism ; *Disease ; Eating ; Epithelium/*metabolism/*microbiology ; Fatty Acids/chemistry/metabolism ; Female ; Fucose/*metabolism ; Fucosyltransferases/metabolism ; Gene Expression Regulation, Bacterial ; Glycosylation ; Immune Tolerance ; Immunity, Innate ; Interleukins/biosynthesis/immunology ; Intestine, Small/*metabolism/*microbiology ; Ligands ; Male ; Metabolic Networks and Pathways/genetics ; Mice ; Microbiota/physiology ; Protective Factors ; *Symbiosis ; Toll-Like Receptors/agonists/immunology/metabolism ; Virulence Factors/genetics

0538-8066

Chemistry ; Physical Chemistry

Wiley InterScience Backfile Collection 1832-2000

Chemistry and Pharmacology

The kinetics of gas-phase reaction of CH3CF2I with HI were studied from 496 to 549K and have been shown to be consistent with the following mechanism: A least squares treatment of the data gave \documentclass{article}\pagestyle{empty}\begin{document}$$\log k_1 (M^{- 1} \cdot \sec ^{- 1}) = (11.4 \pm 0.3) - \frac{{(15.7 \pm 0.8)}}{\theta}$$\end{document} where θ = 2.303 RT kcal/mole. The observed activation energy E1 was combined with E2 = 0 ± 1 kcal/mole to yield \documentclass{article}\pagestyle{empty}\begin{document}$$DH^ \circ ({\rm CH}_{\rm 3} {\rm CF}_2 - {\rm I}) = 52.1 \pm 1.0{\rm kcal}/{\rm mole}$$\end{document} The result, combined with data for several C—I bond dissociation energies, leads us to conclude that the C(sp3)—I bond is relatively insensitive to F for H substitution and that the C(sp2)-I bond has considerable double-bond character.

2 Ill.

Electronic Resource

0538-8066

Chemistry ; Physical Chemistry

Wiley InterScience Backfile Collection 1832-2000

Chemistry and Pharmacology

The kinetics and equilibrium of the gas-phase reaction of CH3CF2Br with I2 were studied spectrophotometrically from 581 to 662°K and determined to be consistent with the following mechanism: A least squares analysis of the kinetic data taken in the initial stages of reaction resulted in log k1 (M-1 · sec-1) = (11.0 ± 0.3) - (27.7 ± 0.8)/θ where θ = 2.303 RT kcal/mol. The error represents one standard deviation. The equilibrium data were subjected to a “third-law” analysis using entropies and heat capacities estimated from group additivity to derive ΔHr° (623°K) = 10.3 ± 0.2 kcal/mol and ΔHrr (298°K) = 10.2 ± 0.2 kcal/mol. The enthalpy change at 298°K was combined with relevant bond dissociation energies to yield DH°(CH3CF2 - Br) = 68.6 ± 1 kcal/mol which is in excellent agreement with the kinetic data assuming that E2 = 0 ± 1 kcal/mol, namely; DH°(CH3CF2 - Br) = 68.6 ± 1.3 kcal/mol. These data also lead to ΔHf°(CH3CF2Br, g, 298°K) = -119.7 ± 1.5 kcal/mol.

1 Ill.

Electronic Resource

0538-8066

Chemistry ; Physical Chemistry

Wiley InterScience Backfile Collection 1832-2000

Chemistry and Pharmacology

The kinetics of the gas-phase reaction of CH3F with I2 have been studied spectrophotometrically from 629 to 710 K, and were determined to be consistent with the following mechanism: A least-squares analysis of the kinetic data taken in the initial stages of reaction resulted in \documentclass{article}\pagestyle{empty}\begin{document}$$ \log k_4 (M^{ - 1} \cdot s^{ - 1}) = (11.3 \pm 0.1) - (30.8 \pm 0.2)/\theta $$\end{document} where θ = 4.575T/1000 kcal/mol. The errors represent one standard deviation. The experimental activation energy E4 = 30.8 ± 0.2 kcal/mol was combined with the assumption E3 = 1 ± 1 kcal/mol and estimated heat capacities to obtain \documentclass{article}\pagestyle{empty}\begin{document}$$ \Delta H_r^\circ (4,g,298K) = 30.0 \pm 1{\rm kcal}/{\rm mol} $$\end{document} The enthalpy change at 298 K was combined with selected thermochemical data to derive \documentclass{article}\pagestyle{empty}\begin{document}$$ DH^\circ ({\rm CH}_{\rm 2} {\rm F} - {\rm H}) = 101.2 \pm 1{\rm kcal/mol} $$\end{document} The kinetic studies of ĊHF2 and CH2F2 have been reevaluated to yield \documentclass{article}\pagestyle{empty}\begin{document}$$ DH^ \circ \left( {{\rm CHF}_{\rm 2} - {\rm H}} \right) = 103.2 \pm 1\,{{{\rm kcal}} \mathord{\left/ {\vphantom {{{\rm kcal}} {{\rm mol}}}} \right. \kern-\nulldelimiterspace} {{\rm mol}}} $$\end{document} These results are combined with literature data to yield the C—H, C—F, and C—Cl bond dissociation energies in their respective fluoromethanes, and the effect of α-fluorine substitution is discussed.

4 Tab.

Electronic Resource