Kinetics and Mechanism of the Aminolysis of Diphenyl Phosphinic Chloride with Anilines

et al. 2008

The deuterium kinetic isotope effects (KIEs) involving deuterated aniline nucleophiles (XC 6 H 4 ND 2 ) are reported for the reactions of dimethyl chlorophosphate (1), dimethyl chlorothionophosphate (2), diethyl chlorophosphate (3) and diethyl chlorothionophosphate (4) in acetonitrile at 55.0 8C. The obtained k H /k D values are 0.798-0.979, 0.945-1.06, 0.714-0.919 and 1.01-1.10 for 1, 2, 3 and 4, respectively. A concerted mechanism with dominant backside nucleophilic attack is proposed for the reactions of 1 and 3. A concerted mechanism involving partial frontside attack through a hydrogen-bonded four-centre-type transition state (TS) is proposed for the reactions of 2 and 4.0.957 AE 0.044 (r ¼ 0.995) a,b Same as in Table 1.Aldrich GR grade dimethyl chlorophosphate (96%), diethyl chlorophosphate (97%), dimethyl chlorothionophosphate (97%) and diethyl chlorothionophosphate (97%) were used without further purification. The other materials are the same as previously described. [19] Kinetics procedureRates were measured conductometrically as described previously. [19,23] [1 and 3] ¼ 2 Â 10 À3 M; [An] ¼ 0.1-0.3 M and [2 and

Kinetics and mechanism of the anilinolysis of dimethyl and diethyl chloro(thiono)phosphates

et al. 2008

Kinetics and mechanism of the aminolysis of dimethyl and methyl phenyl phosphinic chlorides with anilines

et al. 2009

The reactions of dimethyl phosphinic chloride (1) and methyl phenyl phosphinic chloride (2) with X-anilines have been studied kinetically in acetonitrile at 15.0 and 55.0 8C, respectively. The deuterium kinetic isotope effects (KIEs) involving deuterated aniline nucleophiles (XC 6 H 4 ND 2 ) are also reported for the same reactions. The obtained KIEs for 1 are secondary inverse (k H /k D ¼ 0.703-0.899 < 1), while those for 2 are primary normal (k H /k D ¼ 1.62-2.10 > 1). A concerted mechanism involving predominantly backside nucleophilic attack is proposed for the anilinolysis of 1. A concerted mechanism involving predominantly frontside attack via a hydrogen-bonded four-center-type transition state is proposed for the anilinolysis of 2. The degree of steric hindrance is the major factor that determines both the reactivity of the phosphinates and the direction of the nucleophilic attack on the phosphinates.

Kinetics and mechanism of the pyridinolyses of dimethyl and diethyl chloro(thiono)phosphates in acetonitrile

et al. 2010

Kinetic studies for the reactions of dimethyl chlorophosphate (1), dimethyl chlorothionophosphate (2), diethyl chlorophosphate (3), and diethyl chlorothionophosphate (4) with substituted (X) pyridines have been carried out in acetonitrile. The pyridinolyses of the P = O systems (1 and 3) show linear free energy correlations for substituent X variations, while those of the P = S systems (2 and 4) show biphasic concave upward Hammett and Brönsted plots with a break region between 3‐phenyl and 3‐methoxy pyridines. A concerted mechanism with both frontside and backside nucleophilic attack is proposed for the reactions of 1 and 3, but the fraction of a frontside attacks is somewhat larger than that of a backside attack. A concerted mechanism with a dominant backside nucleophilic attack for weakly basic pyridines and a concerted mechanism with a dominant frontside nucleophilic attack for strongly basic pyridines are proposed for the reactions of 2 and 4. The pyridinolysis rate does not depend solely on one major factor. The concave upward free energy relationship can be diagnostic of a change in the direction of the nucleophilic attack. Copyright © 2010 John Wiley & Sons, Ltd.