ChemInform Abstract: KINETICS OF PROTON TRANSFER REACTIONS OF CARBON ACIDS PART 5, VARIATION OF PRIMARY DEUTERIUM ISOTOPE EFFECT WITH SOLVENT COMPOSITION FOR THE REACTION OF DI-(4-NITROPHENYL)METHANE WITH T-BUTOXIDE IN T-BUTYL ALCOHOL-TOLUENE MIXTURES

1975 ◽  
Vol 6 (29) ◽  
pp. no-no
Author(s):  
ARNOLD JARCZEWSKI ◽  
PRZEMYSLAW PRUSZYNSKI ◽  
KENNETH T. LEFFEK
Keyword(s):  
Proton Transfer ◽  
Isotope Effect ◽  
Butyl Alcohol ◽  
Solvent Composition ◽  
Transfer Reactions ◽  
Deuterium Isotope Effect ◽  
Proton Transfer Reactions ◽  
Carbon Acids ◽  
Kinetics Of

Kinetics of Proton Transfer Reactions of Carbon Acids. IV. Primary Deuterium Isotope Effect in the Reaction of Di-(4-nitrophenyl)methane-d2 with t-Butoxide

1974 ◽  
Vol 52 (4) ◽  
pp. 592-596 ◽  
Author(s):  
Jae-Hang Kim ◽  
Kenneth T. Leffek
Keyword(s):  
Proton Transfer ◽  
Isotope Effect ◽  
Activation Parameters ◽  
Proton Transfer Reaction ◽  
Transfer Reactions ◽  
Deuterium Isotope Effect ◽  
Enthalpy Of Activation ◽  
Proton Transfer Reactions ◽  
Carbon Acids ◽  
Kinetics Of

The primary deuterium isotope effect has been measured for the proton transfer reaction from di-(4-nitrophenyl)methane to t-butoxide ion in a solvent consisting of 10% v/v toluene in t-butanol at a series of temperatures between 20 and 45 °C. The isotopic rate ratio, kH/kD, is 7.3 at 25 °C. The activation parameters showed an enthalpy of activation difference (ΔHD≠ − ΔHH≠) of only ca. [Formula: see text] kcal mol−1 and an entropy isotope effect (ΔSD≠ − ΔSH≠) of −2.4 cal mol−1 deg−1. The latter indicates, according to the theory of Bell, that tunnelling of the proton through the energy barrier is unimportant in this reaction. This result is compared to other reactions in the literature, in which tunnelling has been postulated to occur.

Kinetics of Proton Transfer Reactions of Carbon Acids. II. Reaction of Di-(4-nitrophenyl)methane with Alkoxide Bases

1972 ◽  
Vol 50 (1) ◽  
pp. 24-30 ◽  
Author(s):  
A. Jarczewski ◽  
K. T. Leffek
Keyword(s):  
Proton Transfer ◽  
Transition State ◽  
Rate Constants ◽  
Activation Parameters ◽  
Transfer Reactions ◽  
Activation Process ◽  
Proton Transfers ◽  
Proton Transfer Reactions ◽  
Carbon Acids ◽  
Kinetics Of

The second-order rate constants have been measured over a range of temperatures for the proton-transter reactions from di-(4-nitrophenyl)methane to ethoxide, isopropoxide, and t-butoxide ions in solvents consisting of the corresponding alcohols containing 10% toluene by volume. The activation parameters ΔH≠ and ΔS≠ have been calculated and an interpretation of them is given in terms of solvation effects during the activation process. A comparison between the activation parameters for proton transfers and E2 olefin-forming β-elimination reactions is made and discussed with respect to transition state character of the latter reactions.

Kinetics of Proton Transfer Reactions of Carbon Acids. V. Variation of Primary Deuterium Isotope Effect with Solvent Composition for the Reaction of Di-(4-nitrophenyl)methane with t-Butoxide in t- Butyl Alcohol–Toluene Mixtures

1975 ◽  
Vol 53 (8) ◽  
pp. 1176-1180 ◽  
Author(s):  
Arnold Jarczewski ◽  
Przemyslaw Pruszynski ◽  
Kenneth T. Leffek
Keyword(s):  
Proton Transfer ◽  
Isotope Effects ◽  
Time Lag ◽  
Activation Parameters ◽  
Proton Transfer Reaction ◽  
Butyl Alcohol ◽  
Proton Transfer Reactions ◽  
Carbon Acids ◽  
Entropy Of Activation ◽  
Kinetics Of

The second-order rate constants, activation parameters, and primary deuterium isotope effects are reported for the proton transfer reaction from di-(4-nitrophenyl)methane to t-butoxide ion in a series of solvents containing varying amounts of toluene in t-butyl alcohol. Increasing toluene content in the solvent decreases the rate constant and increases the enthalpy of activation, while the entropy of activation becomes less negative. The isotope rate ratio kH/kD increases from 7.3 in 10% v/v toluene to 9.4 in 50% v/v toluene at 25 °C, corresponding to a change in (ΔHD≠ − ΔHH≠) from 0.46 to 1.0 kcal mol−1 and a change in (ΔSD≠ − ΔSH≠) from −2.4 to −1.1 cal mol−1 deg−1. It is suggested that the negative values for (ΔSD≠ − ΔSH≠) are due to a time lag for solvent reorganization relative to the proton transfer.

Proton transfer reactions from 4-X-phenyl-4-nitrophenylcyanomethanes to tetramethylguanidine in acetonitrile solvent

1984 ◽  
Vol 62 (12) ◽  
pp. 2653-2656 ◽  
Author(s):  
Mahmood Hojatti ◽  
Kenneth T. Leffek
Keyword(s):  
Proton Transfer ◽  
Isotope Effect ◽  
Equilibrium Constants ◽  
Transfer Reactions ◽  
Deuterium Isotope Effect ◽  
Proton Transfer Reactions

The reactions of 4-X-phenyl-4-nitrophenylcyanomethanes with tetramethylguanidine in acetonitrile solvent give carbanionic products absorbing in the range λmax 580–650 nm. The equilibrium constants are all large, in excess of 6000 dm3 mol−1. For a series of deprotonation reactions with X = NO2, Cl, Br, H, and OCH3, the Hammett ρ value is 2.03 ± 0.03. For the same compounds, the primary deuterium isotope effect, kH/kD, varies from 8.9 for X = NO2 to 14.0 for X = OCH3 at 25 °C.

Kinetics of Proton-transfer Reactions

Nature ◽  
1967 ◽  
Vol 213 (5071) ◽  
pp. 65-66 ◽  
Author(s):  
G. C. BARKER ◽  
D. C. SAMMON
Keyword(s):  
Proton Transfer ◽  
Transfer Reactions ◽  
Proton Transfer Reactions ◽  
Kinetics Of
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