• Bulletin of the Korean Chemical Society
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• v.25 no.9
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• pp.1346-1350
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• 2004

Pseudo-first order rate constants $(k_{obs})$ are reported for the following solvolyses in approximately isodielectric mixtures: 3- and 4-methoxybenzyl chloride, bromo- and chlorodiphenylmethane, and 4-chloro-, 4,4'-dichloro and 4-methyl-chlorodiphenylmethane in 0-80% v/v nitromethane-methanol mixtures; and bromo- and chlorodiphenylmethane and 4-methyl-chlorodiphenylmethane in various acetonitrile-methanol mixtures (in the range 0-50% v/v) at$25^{\circ}C.$ These data, and literature data for t-butyl halides (Cl, Br, and I), and for p-methoxybenzoyl chloride, show rate maxima in solvent compositions of ca. 30% aprotic cosolvent, explained by a stoichiometric solvent effect on electrophilic solvation. Linear relationships are observed between $(k_{obs})/[MeOH]^2$ and [AP]/[MeOH], where [AP] refers to the molar concentration of aprotic cosolvent. The results are consistent with competing third order contributions to $k_{obs}$, $k_{MM}[MeOH]^2$ with hydrogen-bonded methanol as electrophile, and $k_{MAP}[MeOH][AP]$ with hydrogen-bonding disrupted by the aprotic solvent.

• Bulletin of the Korean Chemical Society
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• v.13 no.6
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• pp.599-605
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• 1992

Rate constants of methanolyses of para-Z-substituted benzenesulfonyl chlorides have been determined in various isodielectric solvent mixtures. A third-order kinetic behavior has been observed in the methanolysis of p-nitrobenzenesulfonyl chloride in methanol-nitromethane mixture from the correlation figure of logarithms of rate constants were plotted against Y-values based on solvolyses of 1-adamantyl tosylate. $S_N1$-$S_N2$ mixing mechanisms are favored by neutral or weak electron-donating and weak electron-withdrawing substituents of p-Z-substituted benzenesulfonyl chlorides in methanol-nitrobenzene mixture. While the methanolyses of para-Z-substituted benzenesulfonyl chlorides in methanol-ethylene glycol solvent mixture are appropriate for $S_N2$ mechanism from the mechanistic criterion by means of m-values.

• The Korean Journal of Food And Nutrition
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• v.8 no.3
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• pp.172-183
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• 1995

The nucleophilic substitution reactions of p-substituted benzyl bromide with l-substituted N,N-dimethylanilines in methanol and acetonitrile binary solvent mixture which is known to an isodielectric solvent system kinetically and the results are as follows. The positive charge is developed on the reaction center of the substrate and it means that the bond cleavage is preceded more than bond formation in the transition state on the analogy of Hammett px values. The bond form3tlon is not progressed in the case of electron donating substituent of substrate. However, the bond formation is much developed in the case of electron withdrawing substituent of substrate on the analogy of Hammett py values. The nucleophilic attacking ability is shown a highest at 80% (V/V) methanol content and the bond formation is well progressed at the same methanol composition on the result of a cross interaction coefficient, pxy. The result of transition state structure that is applicated to the potential energy surface model is in accord with the result that Is applicated to the reaction susceptibilities. The reaction Is subject to the polarity-polarizability term more than the hydrogen bond donor acidity term by application to the solvatochromic parameter eouation.

• Journal of the Korean Chemical Society
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• v.41 no.2
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• pp.63-68
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• 1997

Calorimetric measurements have been carried out for the binary mixture between protic, ROH (R=Me, Et) and dipolar aprotic solvents, MeCN,$Me_2CO,\;MeNO_2(or EtNO_2)$in order to investigate the molecular interaction and liquid structure of isodielectric solvents. From the measured partial molar enthalpies of the solutions, excess enthalpies for the mixing process were determined. The hydrogen bond strength between two components decreases in the order of$ROH-ROH>ROH-Me_2CO>ROH-MeCN>ROH-MeNO_2(or EtNO_2)$and the hydrogen bond donor acidity decreases in the order of MeOH>EtOH. From this result, we can conclude that the most important interaction for the formation of binary liquid mixture comes from the specific hydrogen bond.