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KMID : 1059519880320040301
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Journal of the Korean Chemical Society
1988 Volume.32 No. 4 p.301 ~ p.310
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Kinetics for Mononuclear Heterocyclic Rearrangement of N-(5-phenyl-1,2,4-oxadiazol-3-yl)-N'-arylformamidine (I)
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Hwang Jung-Ui
Chung Jong-Jae
Youn Young-Zoo
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Abstract
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Reaction rates for mononuclear heterocyclic rearrangement of N-(5-phenyl-1,2,4-oxadiazol-3-yl)-N'-arylformamidines into 3-acylamino-1-aryl-1,2,4-triazoles were determined spectrophotometrically in dioxane/water (50 : 50, v/v). There are two different reaction paths according to pH. One is pH-independent path, the other is pH-dependent one. In pH-independent path, the result of substituent effect by IYT equation show that N-H bond breaking as well as new N-N bond formation controls the reaction rate. In pH-dependent path, concave-upward Hammett plot was observed. It can be concluded that new N-N bond formation is more advanced than N-H bond breaking in transition state for electron-donating substituents, but N-H bond breaking is more advanced than new N-N bond formation for electron-withdrawing substituents.
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