Accession Number : AD0618834

Title :   ELECTRON SPIN RESONANCE AND POLAROGRAPHIC INVESTIGATION OF SUBSTITUTED NITROBENZENE NEGATIVE IONS,

Corporate Author : HARVARD UNIV CAMBRIDGE MASS DEPT OF CHEMISTRY

Personal Author(s) : Maki,August H. ; Geske,David H.

Report Date : 29 SEP 1960

Pagination or Media Count : 9

Abstract : Electron spin resonance spectra were obtained for 14 para substixted nitrobenzene mononegative ions that were generated in acetonitrile solution by electrochemical reduction within a microwave cavity. Polarographic data were also obtained for these para substituents and for 8 meta substituents. An excellent linear correlation was found between the half-wave potentials for the meta substituents and sigma-n and sigma-o values. From gross deviation of p-ni.o and p-amino substituents from the meta correlation line, para resonance energies are estimated. The N14 coupling constant of the nitro group is found to decrease as the ease of reducing the parent molecule is increased by the para substitution and vice versa. Measurement of ring proton coupling constants leads to the conclusion that the total electron spin magnetization in the four central ring pi-orbitals is approximately constant. The para substituent merely effects a redistribution of the magnetization among these ring positions. Evidence based on hyperfine structure is presented for hindered rotation of the aldehyde group of para nitrobenzaldehyde anion, and a maximum rotational frequency of 2,800,000 c.p.s. is estimated. Comparison of the F19 hyperfine coupling constant of p-fluoronitrobenzene with the para proton coupling constant of nitrobenzene leads to the ratio F to H coupling constants = 2.12; from this ratio is estimated that Q-F = 47.5. (Author)

Descriptors :   (*NITROBENZENES, FREE RADICALS), (*FREE RADICALS, NITROBENZENES), (*MICROWAVE SPECTROSCOPY, NITROBENZENES), (*POLAROGRAPHIC ANALYSIS, NITROBENZENES), NUCLEAR MAGNETIC RESONANCE, ABSORPTION SPECTRA, IONS, ELECTROCHEMISTRY, REDUCTION(CHEMISTRY), ATOMIC ORBITALS, HYPERFINE STRUCTURE, ALDEHYDES, FLUORINE COMPOUNDS

Distribution Statement : APPROVED FOR PUBLIC RELEASE