Infrared behavior of heterocycles (bases for photographic sensitizers) according to the nature of the heteroatom and the substituents was written by Bassignana, P.;Cogrossi, C.;Gandino, M.. And the article was included in Chimie et Industrie (Paris) in 1963.Electric Literature of C9H9NO This article mentions the following:
A number of instances are given in which IR frequency shifts of the out-of-plane CH deformation of a 5-membered heterocyclic ring can be correlated with the electronegativity of the heteroatom. The successive introduction of functional groups R, electron donors and acceptors, into position 5 or 6 in the aromatic ring produces out-of-plane vibration displacements of the CH adjacent to the substituted C. A decrease of ν of the nearby CH groups corresponds to a decrease of electronegativity of the heteroatom. This is true of benzo- and 2-methylbenzo derivatives Changes occur when a 2nd heteroatom is introduced in a β position to that of the 1st hetero-atoms (oxazole, thiazole, selenazole). The vibrations then are influenced by the 2 heteroatoms. In keeping the same heteroatom (N) in the 3-position in the heterocyclic nucleus, and in changing the heteroatom in position 1, it is not possible to trace a straight line on a plot of frequency vs. electronegativity according to the Pauling electronegativity series. In effect, a broken line occurs, to which corresponds the min. value of the frequency of out-of-plane CH deformation when the 2nd heteroatom is N. An increase in CH frequency deformation with a decrease in-electronegativity is established (except when the 2nd heteroatom is N). In the experiment, the researchers used many compounds, for example, 2,5-Dimethylbenzoxazole (cas: 5676-58-4Electric Literature of C9H9NO).
2,5-Dimethylbenzoxazole (cas: 5676-58-4) belongs to benzoxazole derivatives. Benzoxazole derivatives have different biological activities. Due to its versatile biological properties, benzoxazole has been incorporated as an essential pharmacophore and substructure in many medicinal compounds.Electric Literature of C9H9NO
Referemce:
Benzoxazole – Wikipedia,
Benzoxazole | C7H5NO – PubChem