Dipole moments and the structure of the molecules of some oxadiazole derivatives
The molecular diagrams of 2-phenyl- and 2,5-diphenyl-1,3,4-oxadiazoles, their derivatives with chlorine, nitro, and dimethylamino substituents in the para positions, 3,5-diphenyl-1,2,4-oxadiazole, and 3,4-diphenyl-1,2,5-oxadiazole have been calculated by the MO LCAO method. In the heterocycle of a substituted oxadiazole there is not, as in aromatic rings, a single system of electrons present in conjugation (the π-electrons of the C=N bond and the pairs of nongeneralized electrons of the oxygen atom). The moment of the C=N bond in the heterocyclic compounds is 2.47 D and is directed from the carbon to the nitrogen. Considerable conjugation occurs between the π-or the p-electrons of the substituents in the phenyl rings of the diphenyloxazoles and the π-electrons of the C=N bonds of the heterocycle.