The absorption spectra of cyclohexyl and cyclohexenyl radicals

✍ Scribed by Robert H. Schuler; Larry K. Patterson

• Publisher: Elsevier Science
• Year: 1974
• Tongue: English
• Weight: 577 KB
• Volume: 27
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(74)90243-7

✦ Synopsis

The absorption spectrum of the cyclohexyl radical exhibits a pronounced shoulder in the region of 250 nm in contrast to the absorption of the cyclopentyl radical which decreases monotonically with increasing wavelength above 220 nm. In this region the cyclohexyl radical absorbs considerably more strongly than does the cyclopentyl radical, e.g., the extinction coefficients of the two radicals are, respectively, 920 and 430 M-' cm-' at 250 nm. The closer proximity of the unpaired electron orbital to the radical skeleton in the non-planar cyclohexyl radical may account for these differences. The cyclohexenyl radical has an intense absorption band centered at 240 nm (E240 = 6500 M-' cm-'). This band, which is obviously associated with a transition involving the n system in this conjugated radical, is considerably broader than the similar but more intense band for the cyclopentenyl radical (widths, respectively of 35 and 20 nm at half maxima). The second order rate constants for disappearance of cyclohexyl and cyclohexenyl radicals have been measured to be (1.2 f 0.4) and (1.6 + 0.2) X 10' M-' set-' , respectively.