Abstract
An analysis of the PMR spectra of benzo- 2,1,3-selenadiazoles and also of compounds containing 2,1,3-oxadiazole and -thiadiazole nuclei has been carried out. It has been shown that the key atoms O, S, and Se ensure the possibility of the establishment of a ring current in the corresponding heterocycles. “Aromaticity” in the sense of a strong ring current in these compounds is somewhat weaker than in naphthalene. The estimates were obtained by calculating the differenceϒ 0 δ ab of the chemical shifts of the protons of the benzene ring linked to the heterocycle from the experimental spectra (A2B2 system) and the subsequent comparison of these data with the theoretical dependence ofϒ 0 δ ABon the distance separating the proton under study and the center of the contour of the ring current. In the case of the benzo-2, 1, 3-X-diazoles (X = O, S, Se), this contour is the heterocyclic ring. Direct measurements of the magnetic susceptibility of these compounds have confirmed the considerable equalization of the bonds in the heterocycle, i.e., the participation of the key atoms O, S, and Se in the formation of the ring system of delocalized electrons. It has been shown that the proposed structural scheme permits the prediction of the magnitudes of the chemical shifts and the PMR spectra of such compounds. The question has been raised of the evaluation of the real acceptor properties (electronegativity) of the key atoms completing the heterocycle.
Similar content being viewed by others
References
B. E. Zaitsev, Z. V. Todres, and V. A. Pozdyshev, KhGS [Chemistry of Heterocyclic Compounds],1, 825, 1965.
E. I. Fedin, Z. V. Todres, and L. S. Efros, KhGS [Chemistry of Heterocyclic Compounds],3, 297, 1967.
M. GotÔ and K. TÔei, Talanta,12, 124, 1955.
J. Pople, W. Schneider, and H. Bernstein, High Resolution Nuclear Magnetic Resonance [Russian translation], IL, Moscow, 134, 1962.
R. W. Hill and L. E. Sutton, J. Chim. Phys.,46, 244, 1949.
S. P. Solodovnikov and Z. V. Todres, KhGS [Chemistry of Heterocyclic Compounds],3, 811, 1967.
D. Ingrain, Free Radicals as Studied by Electron Spin Resonance [Russian translation], IL, Moscow, 190, 1961.
D. Dal Monte and E. Sandri, Ann. chim.,54, 486, 1964.
E. S. Levin, Z. I. Fodiman, and Z. V. Todres, Elektrokhimiya,2, 175, 1965.
V. Sh. Tsveniashvili, Z. V. Todres, and S. I. Zhdanov, ZhOKh,38, 1968.
Ya. G. Dorfman, A. I. Kitaigorodskii, O. L. Lependina, Z. V. Todres, and E. I. Fedin, Abstracts of Papers at the Second All-Union Conference on the Study of Structure and Reactivity by Physical Methods [in Russian], Frunze,266, 1966.
J. Musher, J. Chem. Phys.,35, 1159, 1961.
Ya. G. Dorfman, Diamagnetism and the Chemical Bond [in Russian], Fizmatgiz, Moscow, 170, 1961.
R. Olofson and J. Michelman, J. Org. Chem.,30, 1854, 1965.
A. Boulton, A. Gripper Gray, and A. Katritzky, J. Chem. Soc., 5958, 1965.
B. Dischler and W. Meier, Z. Naturforsch.,16a, 318, 1961.
J. Emsley, J. Feeney, and L. Sutcliffe, High Resolution Nuclear Magnetic Resonance Speetroscopy, N.Y.,1, 1965.
L. Weinstock, P. Davis, D. Mulvey, and J. Schaeffer, Angew. Chem.,79, 315, 1967.
Author information
Authors and Affiliations
Additional information
For part IV, see [6].
Rights and permissions
About this article
Cite this article
Fedin, E.I., Todres, Z.V. Studies in the field of aromatic heterocycles. Chem Heterocycl Compd 4, 308–313 (1968). https://doi.org/10.1007/BF00755265
Issue Date:
DOI: https://doi.org/10.1007/BF00755265