A classical but new kinetic equation for hydride transfer reactions

Abstract

A classical but new kinetic equation to estimate activation energies of various hydride transfer reactions was developed according to transition state theory using the Morse-type free energy curves of hydride donors to release a hydride anion and hydride acceptors to capture a hydride anion and by which the activation energies of 187 typical hydride self-exchange reactions and more than thirty thousand hydride cross transfer reactions in acetonitrile were safely estimated in this work. Since the development of the kinetic equation is only on the basis of the related chemical bond changes of the hydride transfer reactants, the kinetic equation should be also suitable for proton transfer reactions, hydrogen atom transfer reactions and all the other chemical reactions involved with breaking and formation of chemical bonds. One of the most important contributions of this work is to have achieved the perfect unity of the kinetic equation and thermodynamic equation for hydride transfer reactions.

Realization of Quantitative Estimation for Reaction Rate Constants Using only One Physical Parameter for Each Reactant

“…[b] Δ G ≠ XH/40 is the activation free energy of the HAT‐reactions, the data (kcal mol −1 ) of which are derived from Eying equation k 2 =(k B T/h)exp(−Δ G ≠ XH/40 /RT). [c] Δ G o XH/40 is molar free energy changes of the HAT‐reactions, the data (kcal mol −1 ) of which are derived from the subtraction of the bond dissociation energy of two substrates (XH and 40H ): Δ G o XH/Y =Δ H o (XH) ‐ Δ H o ( 40H ), because the entropy change of the reactions with the type of XH+Y→X+YH in acetonitrile (Δ S o XH/Y ) has been verified to be or quite close to zero . The values of Δ H o (XH) and Δ H o ( 40H ) all can be derived from our previous publications …”

“…The new kinetic equation (eq 3) was named as Zhu's kinetic equation . The validity of eq 3 has received strong verification by safely predicting the activation free energy and the corresponding kinetic isotopic effect values of various hydride transfer reactions in acetonitrile at 298 K …”

Unusual Reaction Constant for Hydride Transfer from a Carbanion to 9‐Arylxanthyliums

“…[14] Furthermore, model data, as a new method, also reasonably confirmed the charge-transfer (CT) complex. [5] Note that for hundreds of simple hydride transfers (only involved with the release and capture of a hydride anion), the reaction constant (ρ) should be positive, owing to negative charge transfer to the hydride acceptor in the rate-determining step, [7,12] which could be also rationalized by the Hammett equation. Recently, we discovered anion) should be positive; this is in contrast to the kinetics results.…”

“…[2][3][4][5][6][7][8][9][10][11] For kinetic problems, a classical but new kinetic equation to estimate activation energies of many hydride-transfer reactions has also been developed. [12] Thermodynamic analysis to elucidate the mechanism has been successfully applied in reaction systems such as caffeine, [6] vitamin C 4 , and carbanions. [7] Kinetics for mechanistic studies have thus become more important.…”

Slow generation of hydrogen sulfide from sulfane sulfurs and NADH models

“…The hydride releasing abilities of HEH and BNAH are 22.2 and 43.5 kJ/mol stronger than that of a very close NADH model in which the 1-substituent in the 1,4-dihydronicotinamide contains a ribose skeleton. 20 We first tested the reaction between HEH and a cysteine-derived polysulfide 1 to see if any meaningful reaction could be observed. The reaction was monitored by TLC and GC.…”