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Internet Electronic Journal of Molecular Design - IEJMD, ISSN 1538-6414, CODEN IEJMAT
| ABSTRACT - Internet Electron. J. Mol. Des. August 2006, Volume 5, Number 8, 460-470 |
Theoretical Studies on the Isomers and Their Stable
Conformations of 2-Butanimine
Yulei Zhang, Xinyi Yu, and Siyu Ma
Internet Electron. J. Mol. Des. 2006, 5, 460-470
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Abstract:
Using the B3LYP/cc-pVDZ method based on the density
functional theory (DFT), the isomers and their
conformations of 2-butanimine are studied in this paper.
Two isomers and four stable conformations are found. The
transition states of isomerization reactions and
transformations from a conformation into another are also
found in the molecular potential energy surface (PES). The
frequency analysis method is used on all of the isomers, the
stable conformations and the transition states to verify
whether they are minima or saddle points. All calculations
are repeated with the MP2/cc-pVDZ method. By means of
B3LYP method combining Becke's three-parameter hybrid
functional method with Lee-Yang-Parr's correlation
functional (LYP) and Berny energy gradient method, all
degrees of freedom of target molecules were optimized at
cc-pVDZ basis set level. The structures of each stationary
point including the minimum points and the possible saddle
points in the PES of 2-butanimine were carried out. All of
the stationary points were confirmed by vibrational
analysis. In order to examine the results, the structural
optimization and vibrational analysis of 2-butanimine were
carried out by using MP2 method with cc-pVDZ basis set.
The results are essentially consistent with that of the DFT
calculations. In the calculations, the charge of each point is
zero and the spin multiplicity is one. Two isomers are
found in the molecular PES of 2-butanimine. Each isomer
has another two stable conformations. The transition states
of isomerization reactions and transformation from a
conformation into another also are found in the molecular
PES of 2-butanimine. There are two isomers (cis-isomer
and trans-isomer, namely isomer 1 and isomer 2
respectively) in the molecular PES of 2-butanimine. Each
isomer has another two stable conformations. The isomer 1
is most stable. Because the steric effect of imino-group N-H
of isomer 2, the energy of the isomer 2 is a little higher
than that of isomer 1 (the difference is 0.689 kJ/mol). There
are three cis-trans-isomerization
reactions of the N2-H3
bond. Because the activation barriers are very high, the
reactions occur difficultly. There are six rotation transition
states in the transformation from a conformation into
another. Because the difference of energy among the
isomers and conformations is very small and the rotation
barriers are very low, it is difficult to distinguish and
determine the structure of 2-butanimine in the synthesis products.
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