High-Level ab Initio Molecular Orbital Calculations of Imine Formation

1998 ◽  
Vol 102 (25) ◽  
pp. 4930-4938 ◽  
Author(s):  
Nathan E. Hall ◽  
Brian J. Smith
Keyword(s):  
Ab Initio ◽  
Molecular Orbital ◽  
Molecular Orbital Calculations ◽  
High Level

Origin of the π-Facial Stereoselectivity in the Addition of Nucleophilic Reagents to Chiral Aliphatic Ketones as Evidenced by High-Level Ab Initio Molecular-Orbital Calculations

2006 ◽  
Vol 1 (6) ◽  
pp. 852-859 ◽  
Author(s):  
Osamu Takahashi ◽  
Katsuyoshi Yamasaki ◽  
Yuji Kohno ◽  
Kazuyoshi Ueda ◽  
Hiroko Suezawa ◽  
...  
Keyword(s):  
Ab Initio ◽  
Molecular Orbital ◽  
Molecular Orbital Calculations ◽  
Aliphatic Ketones ◽  
Nucleophilic Reagents ◽  
High Level

Photochemical nucleophile–olefin combination, aromatic substitution (photo-NOCAS) reaction, Part 12. Factors controlling the regiochemistry of the reaction with alcohol as the nucleophile

1996 ◽  
Vol 74 (11) ◽  
pp. 2143-2166 ◽  
Author(s):  
Donald R. Arnold ◽  
Mary S. W. Chan ◽  
Kimberly A. McManus
Keyword(s):  
Ab Initio ◽  
Molecular Orbital ◽  
Radical Cations ◽  
Major Product ◽  
Convincing Evidence ◽  
Molecular Orbital Calculations ◽  
Aromatic Substitution ◽  
Intermediate Radical ◽  
High Level ◽  
Allylic Radical

The photo-NOCAS reaction that combines methanol, serving as the nucleophile, and the radical cation of 4-methyl-1,3-pentadiene (14+•), substituting on the 1,4-dicyanobenzene radical anion (1−•), yields (E)-1-(4-cyanophenyl)-4-methoxy-4-methyl-2-pentene (15) as the major product. This regioisomer arises from bonding of methanol to C-4, the more heavily alkyl-substituted carbon of the diene, giving the less alkyl-substituted allylic radical. All previous examples of the photo-NOCAS reaction have yielded major adduct(s) having regiochemistry consistent with the anti-Markovnikov rule; the more heavily substituted (more stable?) β-alkoxyalkyl radical was the predominant intermediate. Empirically derived heats of formation and high-level ab initio molecular orbital calculations (MP2/6-31G*//HF/6-31G*) provide convincing evidence that of the two alternative allylic radicals, generated upon addition of methanol to 14+•, that which has the more alkyl substituted allylic radical moiety is, in fact, not the more stable. Of course, the total structure of the intermediate must be considered; the stabilizing effect of alkyl substitution on the carbon next to the oxygen of the ether moiety cannot be ignored. Ab initio molecular orbital calculations (MP2/6-31G*//HF/6-31G*) are reported for the radical cations of 2-methylpropene (2+•), 2-methyl-2-butene (6+•), 2-methyl-1,3-butadiene (9+•), 4-methyl-1,3-pentadiene (14+•), and 2,4-dimethyl-1,3-pentadiene (18+•) Calculations were also carried out on possible intermediates (bridged radical cations, distonic radical cations, and β-alkoxyalkyl radicals) involved upon reaction of these radical cations with methanol. Results of these calculations provide a basis for explaining/predicting the regiochemistry of the photo-NOCAS reaction involving methanol as the nucleophile: the major adduct(s) result(s) from attachment of methanol to that end of the alkene or diene which gives rise to the more stable intermediate radical. The more stable radical is not necessarily the more heavily alkyl substituted. Key words: photoinduced electron transfer, radicals, radical cations, ab initio molecular orbital calculations.

A pairwise additivity scheme for conformational energies of substituted ethanes

1975 ◽  
Vol 343 (1632) ◽  
pp. 1-10 ◽  
Keyword(s):  
Large Deviations ◽  
Ab Initio ◽  
Dihedral Angle ◽  
Molecular Orbital ◽  
Methyl Groups ◽  
Molecular Orbital Calculations ◽  
Linear Combinations ◽  
Strongly Interacting ◽  
Conformational Energies

Ab initio molecular orbital calculations are used to explore additivity in the conformational energies of poly-substituted ethanes in terms of conformational energies of ethane and appropriate mono- and 1,2-di-substituted derivatives. Such relations would allow complex calculations for poly-substituted ethanes to be replaced by much simpler ones on a small number of parent molecules. General expressions for the linear combinations are derived from the assumption that interactions between vicinal substituents are pairwise additive and depend only on the vicinal dihedral angle. The additivity scheme is tested for 15 ethanes, di-, tri- or tetrasubstituted by cyano and methyl groups and for a smaller number of fluoroethanes. Additivity applies to within 0.1- 0.3 k J mol -1 in the methylethanes and mostly to within about 0.7- 0.8 kJ mol -1 in cyanoethanes. Large deviations are found among the geminally substituted fluoroethanes. It is suggested that the additivity approximation is most successful in the absence of strongly interacting geminal groups. Predictions are made of conformational energies of ten hexa(cyano- and methyl-) substituted ethanes.

Ab initio molecular orbital calculations on the water-carbon dioxide system: Molecular complexes

1975 ◽  
Vol 30 (1) ◽  
pp. 58-59 ◽  
Author(s):  
B. Jönsson ◽  
G. Karlström ◽  
H. Wennerström
Keyword(s):  
Carbon Dioxide ◽  
Ab Initio ◽  
Molecular Orbital ◽  
Molecular Complexes ◽  
Molecular Orbital Calculations

Gas-Phase Tautomerism in the Triazoles and Tetrazoles: A Study by Photoelectron Spectroscopy and ab Initio Molecular Orbital Calculations

1981 ◽  
Vol 36 (11) ◽  
pp. 1246-1252 ◽  
Author(s):  
Michael H. Palmer ◽  
Isobel Simpson ◽  
J. Ross Wheeler
Keyword(s):  
Ab Initio ◽  
Gas Phase ◽  
Molecular Orbital ◽  
Photoelectron Spectroscopy ◽  
Relative Stability ◽  
Photoelectron Spectra ◽  
Equilibrium Geometry ◽  
Molecular Orbital Calculations ◽  
Methyl Derivatives

The photoelectron spectra of the tautomeric 1,2,3,- and 1,2,4-triazole and 1,2,3,4-tetrazole systems have been compared with the corresponding N-methyl derivatives. The dominant tautomers in the gas phase have been identified as 2 H-1,2,3-triazole, 1 H-1,2,4-triazole and 2H-tetrazole.Full optimisation of the equilibrium geometry by ab initio molecular orbital methods leads to the same conclusions, for relative stability of the tautomers in each of the triazoles, but the calculations wrongly predict the tetrazole tautomerism.

Proposal of selective inhibitor for bacterial zinc metalloprotease: Molecular mechanics and ab initio molecular orbital calculations

2021 ◽  
pp. 108047
Author(s):  
Kyohei Imai ◽  
Ryosuke Saito ◽  
Takuya Ezawa ◽  
Satoshi Sugiyama ◽  
Ingebrigt Sylte ◽  
...  
Keyword(s):  
Ab Initio ◽  
Molecular Mechanics ◽  
Molecular Orbital ◽  
Selective Inhibitor ◽  
Molecular Orbital Calculations ◽  
Zinc Metalloprotease

Prediction of Charge Transport Properties of Molecular Materials by Ab Initio Molecular Orbital Calculations

2000 ◽  
Vol 660 ◽  
Author(s):  
Wataru Sotoyama ◽  
Tomoaki Hayano ◽  
Hiroyuki Sato ◽  
Azuma Matsuura ◽  
Toshiaki Narusawa
Keyword(s):  
Charge Transport ◽  
Ab Initio ◽  
Molecular Orbital ◽  
Electron Mobility ◽  
Molecular Orbital Calculations ◽  
Molecular Materials ◽  
Structural Reorganization ◽  
Charge Hopping ◽  
Reorganization Energies ◽  
A Charge

ABSTRACTWe developed a method to predict the charge transport (CT) type (hole or electron) in molecular materials that uses molecular orbital calculations. The hole-and-electron-mobility ratios of molecular materials were calculated based on molecular structural reorganization energies in a charge hopping process. The CT types predicted from the calculated mobility ratios agreed with those experimentally obtained in seven of the eight model molecules.

Quantum Monte Carlo and high-level ab initio molecular orbital investigation of dissociation channels of the positronic alkali-metal hydrides, [XH;e+] (X = Li, Na, and K)

2014 ◽  
Vol 68 (3) ◽  
Author(s):  
Yurika Yamada ◽  
Yukiumi Kita ◽  
Masanori Tachikawa ◽  
Mike D. Towler ◽  
Richard J. Needs
Keyword(s):  
Monte Carlo ◽  
Alkali Metal ◽  
Ab Initio ◽  
Molecular Orbital ◽  
Quantum Monte Carlo ◽  
Metal Hydrides ◽  
High Level
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