• Bulletin of the Korean Chemical Society
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• v.22 no.8
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• pp.842-846
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• 2001

Solvolyses of N-methyl-N-phenylcarbamoyl chlorides in aqueous binary mixtures of acetone, ethanol, methanol and in water, D2O, and 50% D2O-CH3OD are investigated at 25.0 $^{\circ}C.$ The Grunwald-Winstein plots of first-ord er rate constants for N-methyl-N-phenylcarbamoyl chlorides with YCl (based on 2-adamantyl chloride) show a dispersion phenomenon. The ring parameter (I) has been shown to give considerable improvement when it is added as an hI term to the original Grunwald-Winstein and extended Grunwald-Winstein correlations for the solvolyses of N-methyl-N-phenylcarbamoyl chlorides. This study has shown that the magnitude of l, m and h values associated with a change of solvent composition is able to predict the dissociative SN2 transition state. The kinetic solvent isotope effects determined in deuterated water are consistent with the proposed mechanism of the general base catalyzed and/or a dissociative SN2 mechanism channel for N-methyl-N-phenylcarbamoyl chlorides solvolyses.

• Bulletin of the Korean Chemical Society
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• v.18 no.9
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• pp.1010-1013
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• 1997

Nucleophilic substitution reactions of (Z)-phenylethyl (X)-benzenesulfonates with (Y)-pyridines were investigated in acetonitrile at 60 ℃ under respective pressures. The magnitudes of the Hammett reaction constants, ρX, ρY and ρZ indicate that a stronger nucleophile leads to a greater degree of bond formation of C-N and a better leaving group is accompanied by a less degree of bond breaking. The magnitude of correlation interaction term, ρij can be used to determine the structure of the transition state (TS) for the SN reaction. As the pressure is increased, the Hammett reaction constants, ρX and |ρY|, are decreased, but correlation interaction coefficient, ρXZ and |ρYZ|, are increased. The results indicate that the reaction of (Z)-phenylethyl (X)-benzenesulfonates with (Y)-pyridines probably moves from a dissociative SN2 to early-type concerted SN2 mechanism by increasing pressure. This result shows that the correlation interaction term ρij can be useful tool to determine the structure of TS, and also the sign of the product ρXZ·ρYZ can be predict the movement of the TS.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.171-171
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• 2009

The electrodes are usually made of a porous mixture of carbon-supported platinum and ionomers. $SnO_2$ particles provide as supports that have been used for DMFCs, and it have high catalytic activities toward methanol oxidation. The main advantage of $SnO_2$ supported electrodes is that it has strong chemical interactions with metallic components. The high activity to a synergistic bifunctional mechanism in which Pt provides the adsorption sites for CO, while oxygen adsorbs dissociative on $SnO_2$. The reaction between the adsorbed species occurs at the Pt/$SnO_2$ boundary. The morphological observations were characterized by FESEM and transmission electron microscopy (TEM). $SnO_2$ particles crystallinity was analyzed by the X-ray diffraction (XRD). The surface bonded state of the $SnO_2$ particles and electrode materials were observed by the X-ray photoelectron spectroscopy (XPS). The electric properties of the Pt/$SnO_2$ catalyst for methanol oxidation have been investigated by the cyclic voltametry (CV) in 0.1M $H_2SO_4$ and 0.1M MeOH aqueous solution. The peak current density of methanol oxidation was increased as the $SnO_2$ content in the anode catalysts increased. Pt/$SnO_2$ catalysts improve the removal of CO ads species formed on the platinum surface during methanol electro-oxidation.