Crystallographic and theoretical investigations of the preferred conformations of three isomeric N-acetyl-dihydro-oxadiazoles

• Published in: Journal of molecular structure Vol. 561; no. 1; pp. 29 - 41
• Main Authors: Carpenter, G.B., Ventura, E., De Morais, L.P.F., Srivastava, R.M., Simas, A.M., Faure, R.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 12-04-2001
• Subjects: B3LYP/6-31G(d) basis set; Conformation; Crystallography; MO calculations; N-Acetyl-dihydro-1,2,4-oxadiazoles; MO calculations; Crystallography; N-Acetyl-dihydro-1,2,4-oxadiazoles; B3LYP/6-31G(d) basis set; Conformation
• ISSN: 0022-2860; 1872-8014
• DOI: 10.1016/S0022-2860(00)00852-8

Structures of three isomeric 2- and 4- acetyl-5-ethyl-3-tolyl-dihydro-1,2,4-oxadiazoles
1–
3 have been determined by X-ray analysis of their single crystals. 2-Acetyl-5-ethyl-3-(
p-tolyl)- and 2-acetyl-5-ethyl-3-(
m-tolyl)-2,5-dihydro-1,2,4-oxaliazoles
1 and
2 are triclinic whereas 4-acetyl-5-ethyl-3-(
p-tolyl)-4,5-dihydro-1,2,4-oxaliazole
3 is monoclinic. Molecular orbital calculations involving semi-empirical method (AM1) and density functional method B3LYP/6-31G(d) were carried out with a view to compare these results with the crystallographic data. The bond lengths, bond angles and torsion angles of all three compounds showed an excellent agreement between the calculated density functional method and crystallographic experimental values.