Kinetics and Mechanism of Pyridinolyses of Ethyl Methyl and Ethyl Propyl Chlorothiophosphates in Acetonitrile 


Vol. 34,  No. 11, pp. 3372-3376, Nov.  2013
10.5012/bkcs.2013.34.11.3372


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  Abstract

The kinetic studies on the reactions of ethyl methyl (2) and ethyl propyl (4) chlorothiophosphates with Xpyridines have been carried out in acetonitrile at 35.0 oC. The free energy correlations with X show biphasic concave upwards with a break point at X = H (2) and 3-Ph (4), respectively. A stepwise mechanism with a ratelimiting leaving group expulsion from the intermediate is proposed based on the magnitudes of selectivity parameters for both substrates. The considerably large values of βX = 1.50(2) and 1.44(4) with strongly basic pyridines and relatively small values of βX = 0.43(2) and 0.36(4) with weakly basic pyridines are interpreted as a change of the attacking direction of the X-pyridines from a frontside to a backside attack toward the chloride leaving group.

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  Cite this article

[IEEE Style]

H. R. Barai and H. W. Lee, "Kinetics and Mechanism of Pyridinolyses of Ethyl Methyl and Ethyl Propyl Chlorothiophosphates in Acetonitrile," Bulletin of the Korean Chemical Society, vol. 34, no. 11, pp. 3372-3376, 2013. DOI: 10.5012/bkcs.2013.34.11.3372.

[ACM Style]

Hasi Rani Barai and Hai Whang Lee. 2013. Kinetics and Mechanism of Pyridinolyses of Ethyl Methyl and Ethyl Propyl Chlorothiophosphates in Acetonitrile. Bulletin of the Korean Chemical Society, 34, 11, (2013), 3372-3376. DOI: 10.5012/bkcs.2013.34.11.3372.

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ISSN(Print) 0253-2964
ISSN(Online) 1229-5949