Nucleophilic substitution reactions of ethyl methyl (2), ethyl propyl (4) and diisopropyl (7) chlorothiophosphates with substituted anilines and deuterated anilines are investigated kinetically in acetonitrile at 55.0 o C. A concerted mechanism is proposed based on the selectivity parameters. The deuterium kinetic isotope effects (DKIEs; k H /k D ) are secondary inverse (k H /k D = 0.66-0.99) with 2, primary normal and secondary inverse (k H / k D = 0.78-1.19) with 4, and primary normal (k H /k

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... D = 1.06-1.21) with 7. The primary normal and secondary inverse DKIEs are rationalized by frontside attack involving hydrogen bonded, four-center-type transition state, and backside attack involving in-line-type transition state, respectively. The anilinolyses of ten chlorothiophosphates are examined based on the reactivity, steric effect of the two ligands, thio effect, reaction mechanism, DKIE and activation parameter. Scheme 1. Anilinolyses of ethyl methyl (2), ethyl propyl (4) and diisopropyl (7) chlorothiophosphates in MeCN at 55.0 o C.