Semi-empirical (PM3 and AM1) and ab initio molecular orbital calculations of 1,2,4-oxadiazoles, 4,5-dihydro-1,2,4-oxadiazoles and 4,4-di-n-butyl-2-phenylbenzo-1,3-oxazine |
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Authors: | Rajendra M Srivastava Wagner M Faustino Ira M Brinn |
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Institution: | a Departamento de Química Fundamental, Universidade Federal de Pernambuco, Cidade Universitária, 50.740-540, Recife, PE, Brazil b Departamento de Química Inorgânica, Instituto de Química, Universidade Federal do Rio de Janeiro, Ilha do Fundão, 21.945-990, Rio de Janeiro, RJ, Brazil |
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Abstract: | Molecular orbital calculations using semi-empirical (PM3 and AM1) and ab initio (HF/6-31G) types have been carried out on several 3,5-disubstituted 1,2,4-oxadiazoles 1a–d, 5-n-butyl-3,5-diaryl-4,5-dihydro-1,2,4-oxadiazoles 2a–d, and 4,4-di-n-butyl-2-phenylbenzo-1,3-oxazine 3. A comparison of the results by the two computational procedures has been made. Transformation of the oxadiazole ring to 4,5-dihydro-1,2,4-oxadiazole having both aryl and n-butyl groups at C-5 exhibited interesting conformational features. Also, examination of 1,3-oxazine 3 gave an idea about the structure of this compound. The rotational barrier of each phenyl group in 1a and 1d has been calculated using the ab initio method HF/6-31G(d). |
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Keywords: | 1 3-Oxazine Ab initio molecular orbital calculations 1 2 4-Oxadiazoles |
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