Semi-empirical Quantum Mechanical, Molecular Orbital Method using Mopac: Calculation of the Arrhenius Parameters for the Pyrolysis of Some Alkyl Acetates

2005 ◽  
Vol 5 (9) ◽  
pp. 1559-1563 ◽  
Author(s):  
I.A. Adejoro ◽  
T.O. Bamkole .
Keyword(s):  
Molecular Orbital ◽  
Quantum Mechanical ◽  
Orbital Method ◽  
Molecular Orbital Method ◽  
Arrhenius Parameters ◽  
Alkyl Acetates ◽  
Semi Empirical

A semi-empirical molecular orbital scheme to study electron transfer in iron–sulphur proteins

2005 ◽  
Vol 33 (1) ◽  
pp. 20-21 ◽  
Author(s):  
M. Sundararajan ◽  
J.P. McNamara ◽  
M. Mohr ◽  
I.H. Hillier ◽  
H. Wang
Keyword(s):  
Electron Transfer ◽  
Electronic Structure ◽  
Molecular Orbital ◽  
Parametric Method ◽  
Orbital Method ◽  
Molecular Orbital Method ◽  
Semi Empirical

We describe the use of the semi-empirical molecular orbital method PM3 (parametric method 3) to study the electronic structure of iron–sulphur proteins. We first develop appropriate parameters to describe models of the redox site of rubredoxins, followed by some preliminary calculations of multinuclear iron systems of relevance to hydrogenases.

Theoretical studies of model compounds of lathyrane-type diterpenes

2004 ◽  
Vol 82 (1) ◽  
pp. 11-18 ◽  
Author(s):  
Yukimasa Terada ◽  
Tomoo Matsuura ◽  
Yukari Mori ◽  
Shosuke Yamamura
Keyword(s):  
Ab Initio ◽  
Molecular Mechanics ◽  
Molecular Orbital ◽  
Theoretical Calculations ◽  
Membered Ring ◽  
Orbital Method ◽  
Methyl Groups ◽  
Molecular Orbital Method ◽  
Stable Conformation ◽  
Semi Empirical

The conformation of the 11-membered ring of the lathyrane skeleton has been investigated using NMR spectra and theoretical calculations. Some other skeletons, such as jatrophane, jatrapholane, and tigliane, seem to be derived from this framework, and the conformation is important in connection with the configuration of the resultant diterpenes. The conformation of lathyrane is principally defined by the orientation of the two methyl groups; namely, the methyl groups on C1 and C6 directed above or below the ring plane. Theoretical calculations revealed that the predominant conformation is altered depending on the oxygen functional groups on the ring. As far as the bond lengths, bond angles, and dihedral angles are concerned, all calculation methods afforded reasonable results. In contrast, as regards conformational stability, only the ab initio molecular orbital method (RHF/6-31G*) predicted the most stable conformation, consistent with NOE experiments. On the other hand, the stable conformations predicted by the ab initio method (RHF/STO-3G), the semi-empirical molecular orbital method (MOPAC(PM3)), and the molecular mechanics calculations (MM3) did not necessarily agree with the conformers suggested by the NOE experiments.Key words: ab initio MO, semi-empirical MO, molecular mechanics, 11-membered ring conformation, NOE.

The correspondence between the resonance and molecular orbital theories

1952 ◽  
Vol 214 (1119) ◽  
pp. 482-493 ◽  
Keyword(s):  
Organic Chemistry ◽  
Molecular Orbital ◽  
Valence Bond ◽  
Quantum Mechanical ◽  
Orbital Method ◽  
Molecular Orbital Method ◽  
Resonance Theory ◽  
Bond Method ◽  
Additional Assumptions

The resonance theory of organic chemistry is critically examined from a theoretical view­point. It is stressed that this theory is not rigorously founded on the quantum-mechanical valence bond method, but involves additional assumptions which cannot be defended. The practical success of the resonance theory must therefore be explained in some other way. It is here shown that a remarkable correspondence exists between the resonance theory and the molecular orbital method; and it is suggested that the resonance theory owes its success more to this correspondence than to the validity of its own premises.

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