Kinetics and Mechanism of the Pyridinolyses of <i>O</i>‐Methyl and <i>O</i>‐Ethyl Phenyl Phosphonochloridothioates in Acetonitrile

The kinetics of the nucleophilic substitution reactions of bis(N,N-diethylamino)phosphinic chloride with substituted anilines (XC6H4NH2) and deuterated anilines (XC6H4ND2) are investigated in MeCN at 65.0°C. The deuterium kinetic isotope effects (DKIEs) are secondary inverse (kH/kD < 1: 0.706–0.947) and the magnitudes of the secondary inverse DKIEs (kH/kD) increase constantly as the nucleophiles are changed from weakly basic to strongly basic anilines. The magnitudes of the selectivity parameters are ρX(H) = –6.34, and βX(H) = 2.24 with substituted anilines and ρX(D) = –6.13 and βX(D) = 2.17 with deuterated anilines. A concerted SN2 mechanism involving predominant backside attack is proposed based on the kH/kD values with substituent X.

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Pyridinolyses of O-Propyl and O-Isopropyl Phenyl Phosphonochloridothioates in Acetonitrile

Barai¹,

Lee

2013

Bulletin of the Korean Chemical Society

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Continuing the kinetic studies on the pyridinolyses of the phosphonochloridothioates, the nucleophilic substitution reactions of O-propyl (4) and O-isopropyl (5) phenyl phosphonochloridothioates with X-pyridines have been carried out kinetically in acetonitrile (MeCN) at 35.0 ± 0.1 ºC (Scheme 1). The kinetic results of the present work are compared with those of the pydidinolyses of1d phosphonochloridothioates, based on the reactivities, selectivity parameters, free energy correlations and reaction mechanisms. Results and DiscussionThe second-order rate constants [k 2 (M -1 s Table 1, together with the selectivity parameters, ρ X and β X . The pyridinolysis rates of 4 are 1.4-1.7 times faster than those of 5. The substituent effects of the nucleophiles on the rates are in consistent with those for a typical nucleophilic substitution reaction with a positive charge development at the nucleophilic N atom in the transition state (TS). The free energy correlations for both 4 and 5, however, exhibit biphasic concave upwards with a break point at X = H (Fig. 1). Similarities of the substituent effects of X on the pyridinolysis rates between 4 and 5 strongly suggest that the pyridinolyses of both 4 and 5 proceed through the same mechanism. The magnitudes of β X [= 2.09 (4) and 2.01 (5) ) and Selectivity Parameters (ρX and βX) of the Reactions of O-Propyl (4) and O-Isopropyl (5) Phenyl Phosphonochloridothioates with X-Pyridines in MeCN at 35.0

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Kinetics and Mechanism of the Pyridinolyses of O‐Methyl and O‐Ethyl Phenyl Phosphonochloridothioates in Acetonitrile

Cited by 5 publications

References 26 publications

Reactions of Carboxylic, Phosphoric, and Sulfonic Acids and Their Derivatives

Reactions of Carboxylic, Phosphoric, and Sulfonic Acids and Their Derivatives

Concerted Pathway to the Mechanism of the Anilinolysis of Bis(N,N-diethylamino)phosphinic Chloride in Acetonitrile

Pyridinolyses of O-Propyl and O-Isopropyl Phenyl Phosphonochloridothioates in Acetonitrile

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