| Summary: | 博士 === 中正理工學院 === 應用化學學系研究所 === 86 === The molecular structures of six positional dinitrophenol
isomers and six positional trinitrophenol isomers were calculated
by ab initio and density function theory (DFT) methods. Calculated
geometrical parameters are in good agreement with the data of
X-ray diffraction. The molecular structure of each isomer is
affected by the position of the substituents. Calculations
revealed that deformations of the phenyl ring and distortions of
the nitro and hydroxyl groups with the phenyl ring of each isomer
are different. Deformations of the phenyl ring do not completely
match the rules predicted by Domenicano et al. It was also found
that distortions of the nitro groups are of significance for
some isomers with nitro groups held close together and these
distortions are mainly affected by the steric effect.The value
of calculated energy is related to the molecular geometry,
especially affected by the steric effect.
Heats of formation of energetic materials can be obtained
either experimentally or theoretically. In order to compare the
results of the two methods, a correlation method was proposed in
this study. The molecular structures and heats of formation of
nitrobenzenes, nitrotoluenes, nitrophenols and nitroanilines
were calculated by AM1 and PM3 methods. Correlation for heat of
formation between the theoretical calculations and experimental
results was evaluated by the weighted least square multivariable
method. Results indicate that there are very precise correlations.
Based on these correlations, the heat of formation of some aromatic
nitro compounds can be predicted without experimental analysis.
Different sensitivities of 2-nitrotoluene (2-NT), 2-nitroaniline
(2-NA), and 2-nitrophenol (2-NP) are of primary concern, although
they have the same intramolecular transfer tautomers of hydrogen
after thermal decomposition. In this study, we present three aci
tautomers of each title molecule in order to rationalize the different
sensitivities among 2-NT, 2-NA, and 2-NP. An ab initio method
with 6-31G* basis set was chosen and after examing the tautomers''
second derivatives, two local minima and a transition state structure
were found in each title molecule. Based on these calculations,
activation energies of thermal decomposition of 2-NT, 2-NA, and
2-NP can be determined and these values are useful to determine
their sensitivities. In this study, we propose the valuable predictions
of heat of formation and calculations of transition state and
activity energy.
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