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Indian Journal of Chemistry -Section A (IJC-A) >
IJC-A Vol.51A [2012] >
IJC-A Vol.51A(04) [April 2012] >
| Title: | Model chemistries of hydrazides. III: SEMO computations of isonicotinic acid hydrazide, its valence isomers and their isopropyl derivatives |
| Authors: | Krishna, K Rama
Rao, Ch V Kameswara
Ramam, V Ananta
Rao, R Sambasiva
Rao, M Venkata Subba |
| Keywords: | Theoretical Chemistry
Hydrazides
Quantum Chemical Paramaters
Optimized Geometries
Isonicotinic Acid Hydrazide
Electron Densities |
| Issue Date: | Apr-2012 |
| Publisher: | NISCAIR-CSIR, India |
| Abstract: | The computational quantum chemistry of isonicotinic acid hydrazide
(INH), an antitubercular drug, is studied at
SEMO level of theory. AMPAC 6.7 package is employed to invoke six hamiltonians,
viz., MNDO, MNDO3, MNDO/C, AM1, PM3 and SAM1, to arrive at the optimized
geometries in the gaseous phase. Picolinic acid hydrazide (PAH), a valence
isomer of INH, and benzoic acid hydrazide (BAH) without a hetero atom in the
aromatic ring and their isopropyl derivatives are also investigated. PAH and
INH are found to be more stable as compared to BAH, based on electronic and
total energies. However, heat of formation is positive (endothermic) and
increases in the order: BAH < INH < PAH. The HOMO concentrates on the
hydrazide fragment, while LUMO extends over the ring. The orbital-based interactions
are more probable with isopropyl derivatives as FMOs spread on either side.
Isopropyl derivatives have higher. (ELUMO - EHOMO) and
electron affinity values, while ionization potential and hardness have lower
values compared to parent compounds. The static dipole moment of INH (1.13
Debye) is substantially increased to 1.87 Debye in isop-INH and to 4.46 Debye in PAH. For INH,
the second order hyperpolarizability is higher than that of PAH. The
electrophilic centers are the terminal nitrogens of hydrazide fragment and the pyridine
nitrogen in INH and PAH. The isopropyl analogues have higher electrophilic
character. The 3D-surface and 2-D contours of total electron density (TED) on TED,
electrostatic potential (ESP) on TED and ESP on ESP along with Mullikan and ESP
charges are analysed. The quantum chemical computed bond characteristics of INH
are in agreement with the X-ray crystallographic data. |
| Page(s): | 571-579 |
| CC License: |  CC Attribution-Noncommercial-No Derivative Works 2.5 India |
| ISSN: | 0975-0975(Online); 0376-4710(Print) |
| Source: | IJC-A Vol.51A(04) [April 2012]
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