Quantum-mechanical tunnelling and the dimensions of energy-barriers in proton-transfer reactions in solution

1965 ◽  
Vol 39 ◽  
pp. 25 ◽  
Author(s):  
E. F. Caldin ◽  
M. Kasparian
Keyword(s):  
Proton Transfer ◽  
Transfer Reactions ◽  
Quantum Mechanical ◽  
Energy Barriers ◽  
Proton Transfer Reactions

The effect of water-mediated catalysis on the intramolecular proton-transfer reactions of the isomers of 5-chlorouracil: a theoretical study

2019 ◽  
Vol 75 (5) ◽  
pp. 554-561
Author(s):  
Jian Zhang ◽  
Xiu Li
Keyword(s):  
Proton Transfer ◽  
Density Functional ◽  
Dft Method ◽  
Intramolecular Proton Transfer ◽  
Transfer Reactions ◽  
Energy Barriers ◽  
Transfer Energy ◽  
Geometrical Structures ◽  
Proton Transfer Reactions ◽  
Mediated Catalysis

The geometrical structures and thermal energies (E), enthalpies (H) and Gibbs free energies (G) of 13 isomers of 5-chlorouracil (5ClU) in the gas and water phases were investigated using the density functional theory (DFT) method at the M06-2X/6-311++g(3df,3pd) level. The isomers of 5ClU can be microhydrated at different molecular target sites. The mono- and dihydrated forms are the most stable in both the gas and water phases, and, because of the intermolecular interactions, the hydrations lead to a degree of change in the stability trend. Two types of isomerizations were considered: the internal H—O bond rotations in which the H atom rotates 180° around the C—O bond and the intramolecular proton-transfer reactions in which an H atom is transferred between an O atom and a neighbouring N atom. The forward and backward energy barriers for isomerizations of nonhydrated 5ClU were calculated. In addition, 16 optimized transition-state structures for water-mediated catalysis on isomerizations of 5ClU were investigated. The forward and backward proton-transfer energy barriers of water-mediated catalysis on isomerizations of 5ClU were obtained. The results indicate that the catalytic effect of two H2O molecules is much greater than that of one H2O molecule in isomerizations of 5ClU.

Perspectives for hybrid ab initio/molecular mechanical simulations of solutions: from complex chemistry to proton-transfer reactions and interfaces

2014 ◽  
Vol 86 (2) ◽  
pp. 105-117 ◽  
Author(s):  
Thomas S. Hofer
Keyword(s):  
Proton Transfer ◽  
Transfer Reactions ◽  
Quantum Mechanical ◽  
Chemical Systems ◽  
Proton Transfer Reactions ◽  
Charge Field ◽  
Complex Chemistry ◽  
Computational Resources ◽  
Solid Liquid ◽  
Mechanical Charge

Abstract As a consequence of the ongoing development of enhanced computational resources, theoretical chemistry has become an increasingly valuable field for the investigation of a variety of chemical systems. Simulations employing a hybrid quantum mechanical/molecular mechanical (QM/MM) molecular dynamics (MD) technique have been shown to be a particularly promising approach, whenever ultrafast (i.e., picosecond) dynamical properties are to be studied, which are in many cases difficult to access via experimental techniques. Details of the quantum mechanical charge field (QMCF) ansatz, an advanced QM/MM protocol, are discussed and simulation results for various systems ranging from simple ionic hydrates to solvated organic molecules and coordination complexes in solution are presented. A particularly challenging application is the description of proton-transfer reactions in chemical simulations, which is a prerequisite to study acidified and basic systems. The methodical requirements for a combination of the QMCF methodology with a dissociative potential model for the description of the solvent are discussed. Furthermore, the possible extension of QM/MM approaches to solid/liquid interfaces is outlined.

Potential energy construction in the diabatic picture for quantum mechanical rate constants of intermolecular proton transfer

2017 ◽  
Vol 19 (25) ◽  
pp. 16857-16866 ◽  
Author(s):  
Yuta Hori ◽  
Tomonori Ida ◽  
Motohiro Mizuno
Keyword(s):  
Proton Transfer ◽  
Rate Constants ◽  
Quantum Dynamics ◽  
Transfer Reactions ◽  
Quantum Mechanical ◽  
Simple Method ◽  
Thermal Rate Constants ◽  
Intermolecular Proton Transfer ◽  
Proton Transfer Reactions ◽  
Dynamics Simulations

We propose a simple method for potential construction in the diabatic picture and the estimation of thermal rate constants for intermolecular proton transfer reactions using quantum dynamics simulations carried out on the constructed potentials.

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