• Bulletin of the Korean Chemical Society
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• 제35권9호
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• pp.2797-2802
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• 2014

Nucleophilic substitution reactions of Y-aryl methyl (8) and Y-aryl propyl (10) chlorothiophosphates with substituted anilines and deuterated anilines are investigated kinetically in acetonitrile at $55.0^{\circ}C$. A concerted mechanism is proposed for 8 based on the negative ${\rho}_{XY}$ (= -0.23) value, while a stepwise mechanism with a rate-limiting leaving group departure from the intermediate is proposed for 10 based on the positive ${\rho}_{XY}$ (= +0.68) value. The deuterium kinetic isotope effects (DKIEs; $k_H/k_D$) are 0.89-1.28 and 0.62-1.20 with 8 and 10, respectively. Primary normal and secondary inverse DKIEs are rationalized by a frontside attack involving hydrogen bonded, four-center-type transition state and backside attack involving in-line-type transition state, respectively.

• Bulletin of the Korean Chemical Society
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• 제35권2호
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• pp.483-488
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• 2014

The nucleophilic substitution reactions of Y-aryl methyl (8) and Y-aryl propyl (10) chlorothiophosphates with X-pyridines are studied kinetically in acetonitrile at $35.0^{\circ}C$. The Hammett and Bronsted plots with X in the nucleophiles for both substrates exhibit biphasic concave upwards with a break region between X = 3-Me and H. The obtained values of the cross-interaction constants (${\rho}_{XY}$) are negative with 8 while positive with 10 despite the same free energy correlations with X for both substrates. A stepwise mechanism with a rate-limiting bond formation is proposed with 8, whereas a stepwise mechanism with a rate-limiting leaving group departure from the intermediate is proposed with 10 based on the sign of ${\rho}_{XY}$, negative and positive with 8 and 10, respectively. A frontside nucleophilic attack is proposed with strongly basic pyridines based on the considerably great magnitudes of ${\rho}_X$ and ${\beta}_X$ values while a backside attack is proposed with weakly basic pyridines based on the relatively small magnitudes of ${\rho}_X$ and ${\beta}_X$ for both substrates.