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.

scholarly journals Proton Transfer Reactions of Carbon Acids. III. Effect of Solvent Change on the Equilibrium and Kinetic Parameters of the Reaction of Di-(4-nitrophenyl)methane with Alkoxide Bases

1973 ◽  
Vol 51 (17) ◽  
pp. 2805-2809 ◽  
Author(s):  
Jae-Hang Kim ◽  
Kenneth T. Leffek
Keyword(s):  
Proton Transfer ◽  
Kinetic Parameters ◽  
Rate Constants ◽  
Equilibrium Constants ◽  
Mixed Solvents ◽  
Activation Parameters ◽  
Transfer Reactions ◽  
Effect Of Solvent ◽  
Proton Transfer Reactions ◽  
Carbon Acids

The equilibrium constants, the second-order rate constants, and the activation parameters have been determined for the proton transfer from di-(4-nitrophenyl)methane to ethoxide ion in a series of mixed solvents containing various amounts of acetonitrile in ethanol. The quantities have been interpreted in terms of the general postulates of the Miller–Parker theory of solvation effects.

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.

Proton transfer reactions between ortho-methyl substituted derivatives of 4-nitrophenylphenylcyanomethane and nitrogen bases in acetonitrile solvent

1988 ◽  
Vol 66 (6) ◽  
pp. 1454-1458 ◽  
Author(s):  
Kenneth T. Leffek ◽  
Przemyslaw Pruszynski
Keyword(s):  
Proton Transfer ◽  
Isotope Effect ◽  
Rate Constants ◽  
Isotope Effects ◽  
Equilibrium Constants ◽  
Activation Parameters ◽  
Transfer Reactions ◽  
Methyl Groups ◽  
Methyl Group ◽  
Proton Transfer Reactions

Equilibrium constants, rate constants, primary deuterium isotope effects, and activation parameters have been measured for the proton transfer reactions in acetonitrile solvent of 4-nitrophenylphenylcyanomethane and 2-methyl-4-nitrophenylphenyl-cyanomethane with tetramethylguanidine base and for the reactions of 2-methyl-4-nitrophenylphenylcyanomethane and 2,6-di-methyl-4-nitrophenylphenylcyanomethane with 1,5-diazabicyclo[5.4.0]undec-7-ene base. Introduction of the ortho-methyl groups in the substrate molecule caused significant reductions in the equilibrium and rate constants. The expected rise in the kinetic primary deuterium isotope effect was not observed when the first ortho-methyl group was introduced, but a 20% increase did accompany the introduction of the second ortho-methyl group. Enthalpy of activation measurements indicated that there was no increase in the proton tunnelling contribution to the isotope effect when the amount of steric hindrance is increased with ortho-methyl groups.

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 between 4-nitrophenylphenylcyanomethanes and cyclic nitrogen bases in acetonitrile solvent

1990 ◽  
Vol 68 (10) ◽  
pp. 1657-1661 ◽  
Author(s):  
Miroslaw Dworniczak ◽  
Kenneth T. Leffek
Keyword(s):  
Proton Transfer ◽  
Isotope Effects ◽  
Equilibrium Constants ◽  
Activation Parameters ◽  
Transfer Reactions ◽  
Nitrogen Bases ◽  
Conjugate Acid ◽  
Proton Transfer Reactions ◽  
Carbon Acids ◽  
Cyclic Nitrogen

3,3,6,9,9-Pentamethyl-2,10-diazabicyclo[4.4.0]dec-1-ene has been synthesized and its proton transfer reactions, together with those of the bases 2,2,6,6-tetramethylpiperidine and 1,2,2,6,6-pentamethylpiperidine, have been studied with the carbon acids 4-nitrophenylphenylcyanomethane and 2-methyl-4-nitrophenylphenylcyanomethane. Equilibrium constants, rate constants, primary deuterium isotope effects, and activation parameters are reported for the reactions in acetonitrile solvent. Values of the pKa in acetonitrile have been measured for the conjugate acid of each base and the Brønsted β value of 0.56 in acetonitrile has been determined for the proton transfer from 4-nitrophenylphenylcyanomethane. Keywords: proton transfer reactions, kinetic isotope effects, cyclic nitrogen bases.

scholarly journals Equilibrium and kinetic study of the proton transfer reactions between nitroalkanes and strong organic bases — phosphazenes in tetrahydrofuran solvent

2010 ◽  
Vol 8 (3) ◽  
pp. 582-586
Author(s):  
Iwona Binkowska ◽  
Włodzimierz Gałęzowski ◽  
Arnold Jarczewski
Keyword(s):  
Proton Transfer ◽  
Kinetic Study ◽  
Activation Parameters ◽  
Transfer Reactions ◽  
Organic Bases ◽  
Proton Transfer Reactions ◽  
Carbon Acids

AbstractProton transfer reactions rates between carbon acids 1-nitro-1-(4-nitrophenyl)ethane (NPNE), 2-methyl-1-nitro-1-(4-nitrophenyl)propane (MNPNP)) and phosphazenes (BEMP, BTPP, P1-t-Oct) in tetrahydrofuran have been measured, and the activation parameters were determined. The results are compared with those previously obtained for P1-t-Bu phosphazene, guanidines and amidines.

Gas-phase proton-transfer reactions of the hydronium ion at 298 K

1979 ◽  
Vol 57 (12) ◽  
pp. 1518-1523 ◽  
Author(s):  
Gervase I. Mackay ◽  
Scott D. Tanner ◽  
Alan C. Hopkinson ◽  
Diethard K. Bohme
Keyword(s):  
Proton Transfer ◽  
Gas Phase ◽  
Rate Constants ◽  
Transfer Reactions ◽  
Flowing Afterglow ◽  
Hydronium Ion ◽  
Proton Transfer Reactions

Rate constants measured with the flowing afterglow technique at 298 ± 2 K are reported for the proton-transfer reactions of H3O+ with CH2O, CH3CHO, (CH3)2CO, HCOOH, CH3COOH, HCOOCH3, CH3OH, C2H5OH, (CH3)2O, and CH2CO. Dissociative proton-transfer was observed only with CH3COOH. The rate constants are compared with the predictions of various theories for ion–molecule collisions. The protonation is discussed in terms of the energetics and mechanisms of various modes of dissociation.

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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