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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
ISSN: 0975-0975(Online); 0376-4710(Print)
Appears in Collections:IJC-A Vol.51A(04) [April 2012]

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