Semiempirical Calculations on Larger Molecules

2003 ◽  
pp. 263-297
Keyword(s):  
Semiempirical Calculations

An ab initio MO study of conformation structure of nicotinamide and its derivatives

1983 ◽  
Vol 48 (7) ◽  
pp. 1842-1853 ◽  
Author(s):  
Stanislav Böhm ◽  
Josef Kuthan
Keyword(s):  
Ab Initio ◽  
Wave Functions ◽  
Semiempirical Calculations ◽  
Rigid Rotor ◽  
Qualitative Similarity ◽  
Ab Initio Mo ◽  
Experimental Findings

Conformation of nicotinamide (I), 3-carbamoylpyridinium (IIa), 1-methyl-3-carbamoylpyridinium (IIb), and 1-methyl-1,4-dihydronicotinamide (IIIa) has been studied in the rigid rotor approximation on the basis of non-empirical STO-3G wave functions. The rotation barriers decrease in the order: IIIa > I ~ IIb > IIa. When confronted with semiempirical calculations, the conformation curves of molecular energy show a better qualitative similarity to the EHT than to NDDO and particularly to CNDO/2 curves. Relation of the calculated characteristics to experimental findings is discussed.

scholarly journals Accelerations in the Lactonization of Trimethyl Lock Systems Are due to Proximity Orientation and not to Strain Effects

2009 ◽  
Vol 2009 ◽  
pp. 1-5 ◽  
Author(s):  
Rafik Karaman
Keyword(s):  
Kinetic Parameters ◽  
Semiempirical Calculations ◽  
Strain Effect ◽  
Strain Effects ◽  
Enzyme Model ◽  
Trimethyl Lock ◽  
Important Enzyme

DFT at B3LYP/6-31G(d,p) and HF at 6-31G and AM1 semiempirical calculations of thermodynamc and kinetic parameters for the trimethyl lock system (an important enzyme model) indicate that the remarkable enhancement in the lactonizations is largely the result of a proximity orientation as opposed to the currently advanced strain effect.

Aromatic propellenes. Part 8.† Semiempirical calculations and DNMR studies of hexakis(pyrazol-1-yl)benzenes

1997 ◽  
pp. 2173-2178 ◽  
Author(s):  
Concepción Foces-Foces ◽  
Antonio L. Llamas-Saiz ◽  
Cristina Fernández-Castaño ◽  
Rosa Ma Claramunt ◽  
Consuelo Escolástico ◽  
...  
Keyword(s):  
Semiempirical Calculations

scholarly journals First-principles and semiempirical calculations for bound-hole polarons inKNbO3

1999 ◽  
Vol 60 (1) ◽  
pp. 1-5 ◽  
Author(s):  
E. A. Kotomin ◽  
R. I. Eglitis ◽  
A. V. Postnikov ◽  
G. Borstel ◽  
N. E. Christensen
Keyword(s):  
First Principles ◽  
Semiempirical Calculations
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