| Autor: |
Keshab Kumar Adhikary, Hai Whang Lee |
| Rok vydání: |
2011 |
| Předmět: |
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| Zdroj: |
Bulletin of the Korean Chemical Society. 32:3947-3951 |
| ISSN: |
0253-2964 |
| Popis: |
Kinetic studies for the reactions of Y-aryl phenyl chlorothiophosphates with X-pyridines have been carried out in acetonitrile at 35.0 oC. The Hammett and Bronsted plots for substituent X variations in the nucleophiles are biphasic concave upwards with a break point at X = 3-Ph, while the Hammett plots for substituent Y variations in the substrates are biphasic concave downwards (and partially upwards) with a break point at Y = H. The signs and magnitudes of the cross-interaction constant (ρ XY) are strongly dependent upon the nature of substituents, X and Y. The proposed mechanism is a stepwise process with a rate-limiting step change from bond breaking with the weaker electrophiles to bond formation with the stronger eletrophiles. The nonlinear free energy correlations of biphasic concave upward plots for substituent X variations in the nucleophiles are rationalized by a change in the attacking direction of the nucleophile from a backside with less basic pyridines to a frontside attack with more basic pyridines. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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