scholarly journals Secondary kinetic isotope effects in bimolecular nucleophilic substitutions. III. Deuterium effects in the Bunte salt reaction of methyl halides and sulfonates

1969 ◽  
Vol 47 (9) ◽  
pp. 1537-1541 ◽  
Author(s):  
G. E. Jackson ◽  
K. T. Leffek
Keyword(s):  
Isotope Effects ◽  
Activation Parameters ◽  
Kinetic Isotope Effects ◽  
Conductivity Measurements ◽  
Nucleophilic Substitutions ◽  
Reaction Conditions ◽  
Methyl Halides ◽  
Kinetic Isotope ◽  
Deuterium Isotope Effects ◽  
The Difference

Secondary kinetic deuterium isotope effects have been measured for the reaction between thiosulfate ion and methyl-d3 halides and sulfonates in 50% v/v ethanol–water. The results are used to extend the correlation of Seltzer of kH/kD with the difference between the polarizabilities of the attacking nucleophile and the leaving group.Dissociation constants for the [NaS2O3]− ion have been determined by conductivity measurements for the reaction conditions and used to calculate the concentration of free thiosulfate ions present in the reaction mixture. The activation parameters ΔH≠ and ΔS≠, based on second order rate constants calculated with respect to the concentration of thiosulfate ion, are reported.

Secondary Kinetic Isotope Effects in Bimolecular Nucleophilic Substitutions. V. The Role of the Solvent in the Reaction Between Methyl Iodide and Pyridine

1972 ◽  
Vol 50 (7) ◽  
pp. 982-985 ◽  
Author(s):  
K. T. Leffek ◽  
A. F. Matheson
Keyword(s):  
Transition State ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
State Structure ◽  
Transition State Structure ◽  
Initial State ◽  
Nucleophilic Substitutions ◽  
Kinetic Isotope ◽  
Deuterium Isotope Effects

Secondary kinetic deuterium isotope effects are presented for the reaction of methyl-d3 iodide and pyridine in four different solvents. Calculations on mass and moment of inertia change with deuteration in the initial state and an assumed tetrahedral transition state, together with internal rotational effects, are used to rationalize the inverse isotope effects. It is concluded from the variation of the isotopic rate ratio, that the transition state structure varies with solvent.

Secondary Kinetic Isotope Effects in Bimolecular Nucleophilic Substitutions. VI. Effect of α and β Deuteration of Alkyl Halides in their Menschutkin Reactions with Pyridine in Nitrobenzene

1972 ◽  
Vol 50 (7) ◽  
pp. 986-991 ◽  
Author(s):  
K. T. Leffek ◽  
A. F. Matheson
Keyword(s):  
Isotope Effects ◽  
Side Reaction ◽  
Kinetic Isotope Effects ◽  
Alkyl Halides ◽  
State Structure ◽  
Transition State Structure ◽  
Nucleophilic Substitutions ◽  
Kinetic Isotope ◽  
Deuterium Isotope Effects ◽  
Rate Ratios

A survey of kinetic, secondary deuterium isotope effects, for α, β, and γ deuterated alkyl halides reacting with pyridine in nitrobenzene solvent has been made. α-Deuterium effects have been measured for eight compounds, β-deuterium effects for four compounds, and one rate ratio for γ-deuteration is reported. The possible errors in the rate ratios for β-deuterated compounds, resulting from the elimination side reaction have been determined. The results are discussed in terms of transition state structure.

Secondary Kinetic Isotope Effects in Bimolecular Nucleophilic Substitutions. IV. The Temperature Dependence of the Deuterium Effect for the Reaction of N,N-Dimethyl-d6-aniline and Methyl p-toluenesulfonate. Correlation of Isotope Effects on Activation Parameters

1971 ◽  
Vol 49 (3) ◽  
pp. 439-446 ◽  
Author(s):  
K. T. Leffek ◽  
A. F. Matheson
Keyword(s):  
Temperature Dependence ◽  
Isotope Effect ◽  
Isotope Effects ◽  
Activation Parameters ◽  
Kinetic Isotope Effects ◽  
Nucleophilic Substitutions ◽  
Kinetic Isotope ◽  
Similar Correlation ◽  
Straight Lines

The temperature dependence of the isotope effect for the reaction of dimethylaniline and dimethyl-d6-aniline with methyl p-toluenesulfonate in nitrobenzene solvent has been measured, yielding the result, (ΔHD* − ΔHH*) = −134 ± 30 cal mole−1, (ΔSD* − ΔSH*) = −0.15 ± 0.09 cal mol–1 degree−1.This result has been compared with 15 other temperature dependence studies by plotting ΔΔH* per D atom vs. TΔΔS* per D atom. The points fall on two clearly separated straight lines. A similar correlation is found for a plot of ΔΔG* per D atom vs. ΔΔH* per D atom.The significance of the correlation is discussed and a possible rationalization, in terms of mechanism and particularly the role of the solvent is given.

SECONDARY KINETIC ISOTOPE EFFECTS IN BIMOLECULAR NUCLEOPHILIC SUBSTITUTIONS: I. DEUTERIUM EFFECTS IN THE BUNTE SALT REACTION

1964 ◽  
Vol 42 (4) ◽  
pp. 851-855 ◽  
Author(s):  
K. T. Leffek
Keyword(s):  
Aqueous Ethanol ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Sodium Thiosulphate ◽  
Deuterium Isotope Effect ◽  
Nucleophilic Substitutions ◽  
Kinetic Isotope ◽  
Deuterium Isotope Effects ◽  
Rate Ratios ◽  
Aqueous Ethanol Solvent

The secondary deuterium isotope effects have been measured for the reaction between sodium thiosulphate and α-deuterated methyl, ethyl, and n-propyl bromide, and also for β- and γ-deuterated n-propyl bromide, in aqueous ethanol solvent. The α-deuterium isotopic rate ratios (kH/kD) are all greater than unity. These unexpected results are discussed with respect to the suggested use of the α-deuterium isotope effect as a test of mechanism in nucleophilic substitutions.

SOME DEUTERIUM KINETIC ISOTOPE EFFECTS: IV. β-DEUTERIUM EFFECTS IN WATER SOLVOLYSIS OF ETHYL, ISOPROPYL, AND tert-BUTYL COMPOUNDS

1960 ◽  
Vol 38 (11) ◽  
pp. 2171-2177 ◽  
Author(s):  
K. T. Leffek ◽  
J. A. Llewellyn ◽  
R. E. Robertson
Keyword(s):  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Alkyl Halides ◽  
Tert Butyl ◽  
Kinetic Isotope ◽  
Deuterium Isotope Effects ◽  
Intramolecular Forces

The secondary β-deuterium isotope effects have been measured in the water solvolytic reaction of alkyl halides and sulphonates for primary, secondary, and tertiary species. In every case the kinetic isotope effect was greater than unity (kH/kD > 1). This isotope effect may be associated with varying degrees of hyperconjugation or altered non-bonding intramolecular forces. The experiments make it difficult to decide which effect is most important.

Measurements of Solvent and Secondary Kinetic Isotope Effects for the Gas-Phase SN2 Reactions of Fluoride with Methyl Halides

1994 ◽  
Vol 116 (8) ◽  
pp. 3609-3610 ◽  
Author(s):  
Richard A. J. O'Hair ◽  
Gustavo E. Davico ◽  
Jale Hacaloglu ◽  
Thuy Thanh Dang ◽  
Charles H. DePuy ◽  
...  
Keyword(s):  
Gas Phase ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Methyl Halides ◽  
Sn2 Reactions ◽  
Kinetic Isotope

The proton transfer reaction between bis(2,4-dinitrophenyl)methane and nitrogen bases in dimethyl sulfoxide and toluene solvents

1991 ◽  
Vol 69 (3) ◽  
pp. 468-473 ◽  
Author(s):  
Arnold Jarczewski ◽  
Grzegorz Schroeder ◽  
Kenneth T. Leffek
Keyword(s):  
Proton Transfer ◽  
Dimethyl Sulfoxide ◽  
Isotope Effects ◽  
Equilibrium Constants ◽  
Activation Parameters ◽  
Kinetic Isotope Effects ◽  
Proton Transfer Reaction ◽  
Kinetic Isotope ◽  
Deuteron Transfer ◽  
Classical Region

Rate constants have been measured for the proton and deuteron transfer reactions of bis(2,4-dinitrophenyl)methane (1) with 1,1,3,3-tetramethylguanidine (TMG) and 1,5-diazabicyclo[5.4.0]undec-7-ene (DBU) in dimethyl sulfoxide (DMSO) and toluene solvents. Equilibrium constants, primary deuterium kinetic isotope effects, and activation parameters are reported. The reaction of 1 with DBU is faster than that with TMG by factors of 5 and 50 in toluene and DMSO respectively. The primary deuterium kinetic isotope effects, kH/kD = 7–9, which are independent of the polarity of the solvent, indicate an uncoupled mechanism of proton transfer and are in the "classical" region with little or no indication of a tunnelling contribution to the enthalpy of activation for these reactions. Key words: proton transfer, bis(2,4-dinitrophenyl)methane, deuterium isotope effects.

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