ii. A. A. Voityuk, L. N. Mazalov, and E. A. Kravtsova, Zh. Strukt. Khim., 24, No. 6, 26 (1983). 12. E. A. Kravtsova, Author's abstract of Candidate's dissertation, Novosibirsk (1977). 13. R. F. Fenske and R. L. Dekoch, Inorg. Chem., ii, No. 3, 437 (1972). 14. N. M. Sinitsyn and A. A. Svetlov, Koord. Khim., 2, No. I0, 1381 (1976). 15. X-Ray Spectra of Molecules [in Russian], Nauka, Novosibirsk (1977). 16. O. E. Z~yagintsev, N. I. Kolbin, A. N. Ryabov, et el., The Chemistry of Ruthenium [in Russian], Nauka, Moscow (1965). ELECTRONIC STRUCTURE OF MOLECULES OF SUBSTITUTED BENZENES BY X-RAY SPECTROSCOPY. I. NITROBENZENE V. D. Yumatov, V. V. Murakhtanov, N. F. Salakhutdinov, A. V. Okotrub, L. N. Mazalov, L. G. Logunova, V. A. Koptyug and G. G. Furin UDC 537.531:535.3+539.194+543.422.8 The electronic structure of the nitrobenzene molecule has been studied by x-ray spectroscopy with the aid of quantum-chemical calculations. The structure of the molecular orbitals of nitrobenzene has been compared with the structure of benzene and nitrogen dioxide. It has been shown in the framework of a fragment-by-fragment analysis that the interaction of the highest occupied ~ orbitals of the benzene ring and the nitro group is weak. INTRODUCTION It was shown in [1-4] that the values of the first and second ionization potentials of substituted aromatic compounds can be calculated on the basis of the ionization potentials of unsubstituted compounds with consideration of the corrections for the resonance and induc- tive influences of the +M substituents. In the case of -M substituents, it was found to be sufficient to take into account only the inductive effect. This allowed advancement of the hypothesis that in a -M-substituted benzene the highest occupied molecular orbitals (MO's) have a small contribution from the atomic orbitals (AO's) of the substituent. One representative of the -M-substituted benzenes is nitrobenzene. In the present work we studied the structure of the occupied MO's of nitrobenzene, as well as the character of the interaction of the orbitals of NO 2 with the c and ~ systems of the benzene ring with the use of x-ray spectroscopy, which makes it possible to determine the composition of the occu- pied MO's [5, 6]. The transitions of electrons from the filled levels of the molecule to one of its core levels, for example, the is level, are detected in this method. In the case of nitrobenzene, the is levels of the carbon, oxygen, or nitrogen atoms appearing in the com- position of the molecule can serve as the core levels. By investigating the x-ray spectra of these atoms, we can evaluate the contributions of their AO's to the MO's of the molecule [5, 6], as well as determine the orbital energies. The x-ray specta of nitrobenzene were recorded for the gaseous phase (Fig. i). The methods used to obtain and calibrate them were described in [7]. RESULTS AND DISCUSSION In order to understand the special features of the electronic interactions in the nitro- benzene molecule, we shall examine the MO's of the C6H6 and NO 2 molecules, whose electronic Institute of Inorganic Chemistry, Academy of Sciences of the USSR, Siberian Branch. Institute of Organic Chemistry, Academy of Sciences of the USSR, Siberian Branch. Trans- lated from Zhurnal Strukturnoi Khimii, Vol. 28, No. 5, pp. 73-80, September-October, 1987. Original article submitted May 19, 1986. 696 0022-4766/87/2805-0696512.50 9 1988 Plenum Publishing Corporation