[en] The nucleophilic substitution reactions of O-ethyl phenyl phosphonochloridothioic with substituted anilines (XC₆H₄NH₂) and deuterated anilines (XC₆H₄ND₂) are kinetically investigated in acetonitrile at 55.0 .deg. C. The deuterium kinetic isotope effects (DKIEs) invariably increase from a secondary inverse DKIE (k_H/k_D = 0.93) to a primary normal DKIE (k_H/k_D = 1.28) as the substituent of nucleophile (X) changes from electron-donating to electron-withdrawing. These can be rationalized by the gradual transition state (TS) variation from a backside to front side attack. A concerted S_N2 mechanism is proposed. A trigonal bipyramidal TS is proposed for a backside attack while a hydrogen-bonded, four-center-type TS is proposed for a front side attack

[en] Kinetic studies of the pyridinolysis (XC_5H_4N) of aryl dithiomethylacetates (CH_3CH _2C(=S)SC_6H_4Z, 1) are carried out in acetonitrile at 60.0 .deg. C. A biphasic Bronsted plot is obtained with a change in slope from a large (βX ≅ 0.8) to a small (βX ≅ 0.2) value at pK_a "o = 5.2, which is attributed to a change in the rate limiting step from breakdown to formation of a zwitterionic tetrahedral intermediate, T"±, in reaction path as the basicity of the pyridine nucleophile increases. This mechanism is supported by the change of the cross-interaction constant ρXZ from a large positive (ρXZ = +1.36) for the weakly basic pyridines to a small negative (ρXZ = -0.22) value for the strongly basic pyridines. The magnitudes of ρZ and activation parameters are also consistent with the proposed mechanism

[en] The nucleophilic substitution reactions of (2R,4R,5S)-(+)-2-chloro-3,4-dimethyl-5-phenyl-1,3,2-oxazaphospholidine 2-sulfide with X-pyridines are investigated kinetically in acetonitrile at 5.0 .deg. C. The free energy relationships for substituent X variations in the nucleophiles exhibit biphasic concave upwards with a break point at X = 3-Ac. Unusual positive ρ_X (= +4.73) and negative β_X (= .0.75) values are obtained with the weakly basic pyridines, and rationalized by the isokinetic relationship with isokinetic temperature at t_ISOKINETIC = 39.3 .deg. C. A concerted mechanism involving a change of nucleophilic attacking direction from a frontside attack with the strongly basic pyridines to a backside attack with the weakly basic pyridines is proposed on the basis of greater magnitudes of selectivity parameters (ρ_X = -6.15 and β_X = 1.11) with the strongly basic pyridines compared to those (ρ_X = 4.73 and β_X = -0.75) with the weakly basic pyridines

[en] Nucleophilic substitution reactions of ethyl methyl (2), ethyl propyl (4) and diisopropyl (7) chlorothiopho-sphates with substituted anilines and deuterated anilines are investigated kinetically in acetonitrile at 55.0 .deg. 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_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 chloro-thiophosphates are examined based on the reactivity, steric effect of the two ligands, thio effect, reaction mechanism, DKIE and activation parameter

[en] The kinetic studies on the reactions of dipropyl chlorophosphate (3O) with substituted anilines (XC₆H₄NH₂) and deuterated anilines (XC₆H₄ND₂) have been carried out in acetonitrile at 55.0 .deg. C. The obtained deuterium kinetic isotope effects (DKIEs: k_H/k_D) are primary normal (k_H/k_D = 1.09-1.01) with the strongly basic anilines while secondary inverse (k_H/k_D = 0.74-0.82) with the weakly basic anilines. The steric effects of the two ligands on the rates are extensively discussed for the anilinolyses of the (R1O)(R2O)P(=O or S)Cl-type chlorophosphates and chlorothiophosphates. A concerted mechanism is proposed with a frontside nucleophilic attack involving a hydrogen-bonded four-center-type transition state for the strongly basic anilines and with a backside attack transition state for the weakly basic anilines on the basis of the DKIEs, primary normal and secondary inverse with the strongly and weakly basic anilines, respectively

[en] The kinetics and mechanism of the pyridinolysis (XC₅H₄N) of diethyl isothiocyanophosphate are investigated in acetonitrile at 55.0 .deg. C. The Hammett and Bronsted plots for substituent X variations in the nucleophiles exhibit the two discrete slopes with a break region between X = 3-Ac and 4-Ac. These are interpreted to indicate a mechanistic change at the break region from a concerted to a stepwise mechanism with rate-limiting expulsion of the isothiocyanate leaving group from a trigonal bipyramidal pentacoordinated intermediate. The relatively large β_X values with more basic and less basic pyridines imply much greater fraction of frontside nucleophilic attack TSf than that of backside attack TSb

[en] The kinetic studies on the reactions of O-methyl (1), O-propyl (3) and O-isopropyl (4) phenyl phosphono-chloridothioates with substituted anilines and deuterated anilines have been carried out in acetonitrile at 55.0 .deg. C. A concerted S_N2 mechanism is proposed for the anilinolyses of 1, 3 and 4. The anilinolysis rates of the phosphonochloridothioates are predominantly dependent upon the steric effects over the inductive effects of the two ligands. The deuterium kinetic isotope effects (DKIEs; k_H/k_D) are primary normal with 1 and 3, while secondary inverse with 4. Primary normal and secondary inverse DKIEs are rationalized by frontside and backside nucleophilic attack transition state, respectively. The DKIEs of the phosphonochloridothioates do not have any consistent correlations with the two ligands

[en] The reactions of diethyl phosphinic chloride (2) with X-anilines are studied kinetically in acetonitrile at 50.0 .deg. C. The steric effect over the inductive effect is the major factor to determine the reactivity and nucleophilic attacking direction. The secondary inverse DKIEs (k_H/k_D = 0.828 . 0.974) involving deuterated aniline (XC₆H₄ND₂) nucleophiles are obtained. The small magnitudes of ρ_X and β_X values and secondary inverse DKIEs suggest a concerted mechanism involving a backside nucleophilic attack. Nucleophilic substitution at a phosphoryl (P=O) or thiophosphoryl (P=S) center generally proceeds either through stepwise mechanism with a trigonal bipyramidal pentacoordinate (TBP-5C) intermediate or a concerted S_N2 mechanism with a TBP-5C transition state (TS). Continuing the studies on phosphoryl transfer reactions, the reactions of diethyl phosphinic chloride [Et₂P(=O)Cl; 2] with substituted anilines (XC₆H₄NH₂) are investigated kinetically in acetonitrile at 50.0 .deg. C (eq 1). The deuterium kinetic isotope effects (DKIEs; k_H/k_D) involving deuterated aniline (XC₆H₄ND₂) nucleophiles are also investigated, since the DKIEs are one of the strong tools to clarify the reaction mechanism

[en] The nucleophilic substitution reactions of diisopropyl chlorothiophosphate with X-pyridines have been kinetically studied in MeCN at 35.0 .deg. C. The Hammett and Bronsted plots for the substituent X variations in the nucleophiles show biphasic concave upwards with a break point at X = 3-Ph. The pyridinolysis rate of 5 exhibits great negative deviation from the Taft plot. A concerted S_N2 mechanism is proposed involving a change of the attacking direction of the X-pyridines from a frontside attack with the strongly basic pyridines to a backside attack with the weakly basic pyridines

[en] The nucleophilic substitution reactions of dibutyl chlorophosphate (3) with substituted anilines (XC₆H₄NH₂) and deuterated anilines (XC₆H₄ND₂) are investigated kinetically in acetonitrile at 55.0 .deg. C. The obtained deuterium kinetic isotope effects (DKIEs: k_H/k_D) are secondary inverse (k_H/k_D = 0.86-0.97) with the strongly basic anilines while primary normal (k_H/k_D = 1.04-1.10) with the weakly basic anilines. The DKIEs, steric effects of the two ligands, activation parameters, cross-interaction constants, variation trends of the k_H/k_D values with X, and mechanism are discussed for the anilinolyses of the nine (R₁O)(R₂O)P(=O)Cl-type chlorophosphates. A concerted mechanism is proposed with a backside nucleophilic attack transition state for the strongly basic anilines and with a front side attack involving a hydrogen-bonded four-center-type transition state for the weakly basic anilines on the basis of the magnitudes, secondary inverse and primary normal, and variation trends of the k_H/k_D values with X