Machine Learning Classification of Disrotatory IRC and Conrotatory Non-IRC Trajectory Motion for Cyclopropyl Radical Ring Opening

Quasiclassical trajectory analysis is now a standard tool to analyze non-minimum energy pathway motion of organic reactions. However, due to the large amount of information associated with trajectories, quantitative analysis...

Atomic-scale studies of chemical and transport processes relevant to propellant combustion

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] Density functional theory (DFT) and correlated molecular orbital electronic structure calculations were used to study the Al + CO2 [subscript arrow] AlO + CO reaction on the electronic ground-state potential-energy surface (PES). Geometries were optimized using DFT (M11/jun-cc-pV(Q+d)Z) and more accurate energies were obtained using the composite Weizmann-1 theory with Brueckner doubles (W1BD). The results comprise the most complete, most systematic characterization of the Al + CO2 reaction surface to date and are based on consistent application of high-level methods for all stationary points identified. The pathways from Al + CO[subscript 2] to AlO + CO on the electronic ground-state PES all involve formation of one or more stable AlCO2 complexes denoted ?-AlCO2, trans-AlCO[subscript 2], and C[subscript 2v]-AlCO[subscript 2], among which [subscript n]-AlCO[subscript 2] and C[subscript 2v]-AlCO[subscript 2] are the least and most stable, respectively. We report a new minimum-energy pathway for the overall reaction, namely formation of [subscript n]-AlCO[subscript 2] from reactants and dissociation of that same complex to products via a bond-insertion reaction that passes through a fourth (weakly metastable) AlCO[subscript 2] complex denoted cis-OAlCO. Natural Bond Orbital analysis was applied to study trends in charge distribution and the degree of charge transfer in key structures along the minimum-energy pathway. The process of aluminum insertion into CO[subscript 2] is discussed in the context of analogous processes for boron and first-row transition metals. ...

Superionic conduction in β-eucryptite: inelastic neutron scattering and computational studies

The inter- and intra-channel correlated motion of lithium along the hexagonalc-axis gives the minimum energy pathway for ion conduction.

Molecule dynamics and combined QM/MM study on one-carbon unit transfer reaction catalyzed by GAR transformylase

Both a molecule dynamic study and a combined quantum mechanics and molecule mechanics (QM/MM) study on Glycinamide ribonucleotide transformylase (GAR Tfase) catalytic mechanism are presented. The results indicate a direct one-carbon unit transfer process but not a stepwise mechanism in this reaction. The residues near the active center can fix the cofactor (N10-formyltetrahydrofolate) and GAR in proper relative positions by a H-bond network. The transition state and the minimum energy pathway are located on the potential energy surface. After all the residues (including H2O molecules) are removed from the system the activation energy has increased from 145.1 kJ/mol to 243.3 kJ/mol, and the formly transfer reaction is very hard to achieve. The interactions between coenzyme, GAR and residues near the reactive center are discussed as well.

Chemical reaction paths

When two molecules react with one another their mutual approach and subsequent structural reorganization have to follow more or less along a minimum energy pathway in the multidimensional parameter space that defines the structure of the reacting system. Information about such paths can be obtained, in principle, by examining how the structural parameters of certain molecules or parts of molecules change in response to perturbations connected with different crystal or molecular environments. In some cases, striking correlations between independent structural parameters describing molecular sub-systems frozen in different environments have been detected. This makes it possible to arrange the individual structures in a sequence that corresponds, in a general sense, to the course of structural changes expected to occur in a chemical reaction. In this way, reaction paths for several prototypal chemical reactions (S N 1, S N 2, nucleophilic addition to carbonyl groups) have been derived.