Compact transition state and asymmetric induction: a theoretical ab initio SCF-CI study of enamine addition to carbonyl compounds

1987 ◽  
Vol 52 (25) ◽  
pp. 5611-5615 ◽  
Author(s):  
Alain Sevin ◽  
Jacques Maddaluno ◽  
Claude Agami
Keyword(s):  
Transition State ◽  
Ab Initio ◽  
Carbonyl Compounds ◽  
Asymmetric Induction

Active Learning Accelerates Ab Initio Molecular Dynamics on Pericyclic Reactive Energy Surfaces

2020 ◽  
Author(s):  
Shi Jun Ang ◽  
Wujie Wang ◽  
Daniel Schwalbe-Koda ◽  
Simon Axelrod ◽  
Rafael Gomez-Bombarelli
Keyword(s):  
Molecular Dynamics ◽  
Potential Energy ◽  
Transition State ◽  
Potential Energy Surface ◽  
Ab Initio ◽  
Energy Surface ◽  
Computational Cost ◽  
Reactive Trajectories ◽  
Dynamics Simulations ◽  
Energy Surfaces

<div>Modeling dynamical effects in chemical reactions, such as post-transition state bifurcation, requires <i>ab initio</i> molecular dynamics simulations due to the breakdown of simpler static models like transition state theory. However, these simulations tend to be restricted to lower-accuracy electronic structure methods and scarce sampling because of their high computational cost. Here, we report the use of statistical learning to accelerate reactive molecular dynamics simulations by combining high-throughput ab initio calculations, graph-convolution interatomic potentials and active learning. This pipeline was demonstrated on an ambimodal trispericyclic reaction involving 8,8-dicyanoheptafulvene and 6,6-dimethylfulvene. With a dataset size of approximately</div><div>31,000 M062X/def2-SVP quantum mechanical calculations, the computational cost of exploring the reactive potential energy surface was reduced by an order of magnitude. Thousands of virtually costless picosecond-long reactive trajectories suggest that post-transition state bifurcation plays a minor role for the reaction in vacuum. Furthermore, a transfer-learning strategy effectively upgraded the potential energy surface to higher</div><div>levels of theory ((SMD-)M06-2X/def2-TZVPD in vacuum and three other solvents, as well as the more accurate DLPNO-DSD-PBEP86 D3BJ/def2-TZVPD) using about 10% additional calculations for each surface. Since the larger basis set and the dynamic correlation capture intramolecular non-covalent interactions more accurately, they uncover longer lifetimes for the charge-separated intermediate on the more accurate potential energy surfaces. The character of the intermediate switches from entropic to thermodynamic upon including implicit solvation effects, with lifetimes increasing with solvent polarity. Analysis of 2,000 reactive trajectories on the chloroform PES shows a qualitative agreement with the experimentally-reported periselectivity for this reaction. This overall approach is broadly applicable and opens a door to the study of dynamical effects in larger, previously-intractable reactive systems.</div>

Nitro–Nitrite Isomerization and Transition State Switching in the Dissociation of Ionized Nitromethane: A Threshold Photoelectron–Photoion Coincidence Spectroscopy Study

2009 ◽  
Vol 15 (2) ◽  
pp. 157-166 ◽  
Author(s):  
Brandon Ferrier ◽  
Anne-Marie Boulanger ◽  
David M.P. Holland ◽  
David A. Shaw ◽  
Paul M. Mayer
Keyword(s):  
Transition State ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Bond Cleavage ◽  
Cleavage Reaction ◽  
Nitrite Ion ◽  
Methyl Nitrite ◽  
Bond Cleavage Reaction ◽  
Entropy Of Activation ◽  
Lower Entropy

Threshold photoelectron–photoion coincidence (TPEPICO) spectroscopy has been employed to investigate the competition between bond cleavage and rearrangement reactions in the dissociation of ionized nitromethane, 1. Modeling TPEPICO breakdown diagrams with a combination of RRKM theory and ab initio calculations at the G3 level of theory allowed the derivation of the activation energy for the isomerisation of 1 to ionized methyl nitrite, 2, 82 kJ mol−1. In addition, evidence was found for a transition state switch in the bond cleavage reaction in 1 leading to CH3• + NO2+. As internal energy increases, the effective transition state for this reaction becomes tighter (i.e. is characterized by a lower entropy of activation, Δ‡S). Fitted thresholds for NO+ and CH2OHO+ ions, originating from the isomeric methyl nitrite ion, are consistent with G3 level ab initio calculations.

An ab initio study of the rearrangement of carbonyl compounds to oxacarbenes

1977 ◽  
Vol 66 (1) ◽  
pp. 298-302 ◽  
Author(s):  
Julianna A. Altmann ◽  
I. G. Csizmadia ◽  
Keith Yates ◽  
Peter Yates
Keyword(s):  
Ab Initio ◽  
Carbonyl Compounds ◽  
Ab Initio Study

Ab initio Cs transition state for the Diels-Alder reaction of acetylene and butadiene

1990 ◽  
Vol 55 (12) ◽  
pp. 3804-3807 ◽  
Author(s):  
James M. Coxon ◽  
Stephen T. Grice ◽  
Robert G. A. R. Maclagan ◽  
D. Quentin McDonald
Keyword(s):  
Transition State ◽  
Ab Initio ◽  
Alder Reaction ◽  
Diels Alder ◽  
Diels Alder Reaction

Recombination of methyl radicals: ab initio potential and transition-state theory calculations

1989 ◽  
Vol 93 (12) ◽  
pp. 4772-4779 ◽  
Author(s):  
Katherine Valenta Darvesh ◽  
Russell J. Boyd ◽  
Philip D. Pacey
Keyword(s):  
Transition State ◽  
Ab Initio ◽  
Transition State Theory ◽  
State Theory ◽  
Methyl Radicals
Sign in / Sign up

Export Citation Format

Share Document