Abstract
This study involved the adoption of the program (Gaussian 03) to use the method of
calculation the total according to the theory of functions density (DFT) and style
(B3LYP) and the use of al-Qaeda (STO-3G) for the purpose of the expense of
dimensional geometric (lengths and angles bond) when the geometry of a balanced,
charges, functions thermodynamic as well as account and classification of
vibrational patterns belonging to the infrared spectrum and the number of (3N-6)
for the three molecules derived from the ring (1,3,4-Thiadiazole) (symbolized by
the acronym A, B, C). It was found that the compound-C have the highest value
Entropy (S0) and heat capacity (Cv), as demonstrated by observing the results that
most of the atoms belonging to the compound-C be less electron density was
largely due to a nitro group substitute effect (-NO2), which is working to
withdrawing the electrons while the compound-B on the contrary.
This in turn shows the effect of a range Methyl group substitute (-CH3) on the
electronic high pushing compared to the other two compounds. The higher
frequencies values for the (N-H) stretch fundamental vibration mode, and most of
the frequencies of higher value to be returned to the compound-C than their
corresponding in other compounds, and may return this result to the same reason
above where the group is working nitro to withdraw electrons, which lead to a
palace in the lengths of bonds and affirmed this interpretation of calculated results
on the geometry where it was noted that most of the bonds, especially nearby the
group substitutes to be shorter than their counterparts in the two compounds the
other two and this will get more valuable the values of frequencies and on the
contrary in the case of substitutes for the group (-CH3) in the boat (B). Also, For
(A, B and C) molecules the calculated some physical properties (ΔHf (in
kcal/mole), μ (in Debye) ,orbital energies (EHOMO, ELUOMO, in eV) and IP (in eV))
by using (semi-empirical method, MINDO/3 model) . The compound–C, it has less
heats of formation, and easier ionization than compound-A and compound-B .
calculation the total according to the theory of functions density (DFT) and style
(B3LYP) and the use of al-Qaeda (STO-3G) for the purpose of the expense of
dimensional geometric (lengths and angles bond) when the geometry of a balanced,
charges, functions thermodynamic as well as account and classification of
vibrational patterns belonging to the infrared spectrum and the number of (3N-6)
for the three molecules derived from the ring (1,3,4-Thiadiazole) (symbolized by
the acronym A, B, C). It was found that the compound-C have the highest value
Entropy (S0) and heat capacity (Cv), as demonstrated by observing the results that
most of the atoms belonging to the compound-C be less electron density was
largely due to a nitro group substitute effect (-NO2), which is working to
withdrawing the electrons while the compound-B on the contrary.
This in turn shows the effect of a range Methyl group substitute (-CH3) on the
electronic high pushing compared to the other two compounds. The higher
frequencies values for the (N-H) stretch fundamental vibration mode, and most of
the frequencies of higher value to be returned to the compound-C than their
corresponding in other compounds, and may return this result to the same reason
above where the group is working nitro to withdraw electrons, which lead to a
palace in the lengths of bonds and affirmed this interpretation of calculated results
on the geometry where it was noted that most of the bonds, especially nearby the
group substitutes to be shorter than their counterparts in the two compounds the
other two and this will get more valuable the values of frequencies and on the
contrary in the case of substitutes for the group (-CH3) in the boat (B). Also, For
(A, B and C) molecules the calculated some physical properties (ΔHf (in
kcal/mole), μ (in Debye) ,orbital energies (EHOMO, ELUOMO, in eV) and IP (in eV))
by using (semi-empirical method, MINDO/3 model) . The compound–C, it has less
heats of formation, and easier ionization than compound-A and compound-B .
Keywords
1
3
4-Thiadiazole ring
DFT study
IR studies
Thermodynamics functions