Kinetic isotope effects of nitrogen and hydrogen in reaction of N-tert-butyl-P-phenylphosphonamidothioic acid with alcohols

Jankowski, Stefan; Mazur, Adam; Nonas, Tomasz; Vokal, Barbara

doi:10.1016/j.jorganchem.2004.09.025

Cited by 1 publication

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“…This conclusion was supported by results of semiempirical calculations on the PM3 level. However, for the reaction with methanol the addition−elimination mechanism cannot be excluded …”

Section: Introductionsupporting

confidence: 79%

The Intermediacy of Metathiophosphonate PhPSO in the Reaction of N-tert-Butyl-P-phenylphosphonamidothioic Acid with Alcohols

Nonas

Jankowski

2004

J. Org. Chem.

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Kinetic studies of the reaction of N-tert-butyl-P-phenylphosphonamidothioic acid (1) with alcohols were carried out in CH2Cl2 by means of 31P NMR spectrometry. The reaction is of the first order with respect to thio acid 1. The first-order rate constant at 30 degrees C increases with increasing methanol concentration below 0.25 M, but otherwise the rate constants are either independent of alcohol concentration (MeOH above 0.25 M, BuOH) or decrease with increasing alcohol concentration (i-PrOH, t-BuOH). The effect of alcohols on the order of the reaction and parameters of activation, as well as results of competition experiments, lead us to the conclusion that reaction of 1 with alcohols occurs by an elimination-addition mechanism involving the association of the thio acid 1 and the alcohol and then formation in the rate-determining step of an encounter complex 2' ' involving metathiophosphonate 4, amine, and alcohol. Metathiophosphonate 4 reacts preferentially with the alcohol as the encounter complex (primary alcohols) or after diffusion apart as a "free" intermediate (hindered alcohols).

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“…This conclusion was supported by results of semiempirical calculations on the PM3 level. However, for the reaction with methanol the addition−elimination mechanism cannot be excluded …”

Section: Introductionsupporting

confidence: 79%