Fluorine-19 hyperfine splittings in the electron spin resonance spectra of fluorinated aromatic free radicals. II. Triphenylmethyl radicals

Abstract

Appendixvalues used in this study. For computational efficiency, these were calculated using the LEMAO-4G representation.Previous work has shown such r's to be systematically close to the 6-Gaussian valuesg The r's for all nonequivalent atoms (with the exception that hydrogen atoms attached to the same heavy atom are given the same r) were varied in steps of 0.01 until the total energy was minimized. Two to three optimization cycles on the complete set result in {'s accurate to 0.003 or better. Final runs were then made with the LEMAO-6G basis using these r values.press.Table V reports the optimum valence shell (9) W.

Isotope effects in the electron spin resonance spectra of deuterated triphenylmethyl radicals

“…The symmetrically deuterated triphenylmethyl radicals listed in Table I were prepared from the corresponding carbinols by methods described previously. [19][20][21] The carbinols were generously provided by Kresge and Pretto.22 The deuterium content of the Various carbinols was checked by an NMR analysis. The NMR spectra were obtained by dissolving the carbinols in anhydrous THE.…”

“…The ESR spectra were obtained with a spectrometer previously described. 19 All the spectra were recorded at or near room temperature (22 °C) in carefully degassed toluene solutions. The optimum concentration of each radical, which produced, simultaneously, adequate signal-to-noise ratios and good resolution, was determined by trial and error.…”

“…All the hfs constants were determined by spectral simulation with a modified SESRS program routine. 19,23 In order to obtain accurate values of the rather small deuterium hfs constants suitable modifications were made by adjusting the grid and sensitivity of the simulated spectra to the coupling constant magnitudes. The simulated spectra were found to be quite sensitive to the relative values of the hfs constants for two or more sets of equivalent nuclei as encountered in these radicals.…”

“…The absolute, as opposed to relative, accuracy of the hfs constants was checked by comparison to previously published15, 16,19,24 values for the unsubstituted triphenylmethyl radical. Our values are within the experimental uncertainties given in these reports and are likely to be at least as accurate, as we were able to resolve 120 out of the 196 theoretical lines in the spectrum.…”

Perfluoroaromatics. Tris(polyfluoroaryl) carbocations

“…2-(?n7o-Vinyl-2-f.YO-hydroxybicyclo[2.2.1]bept-5-ene (21) was obtained by glc separation of the products from the solvolysis of 16b: nmr 6.40 -* 5.65 (3 H, complex consisting of a multiplet at 6.10 for the endocyclic vinyl proton (2 H), and four singlets for the single vinyl proton), 5.38, 5.13, and 4.93 (d, 2 H, terminal vinyl CH2), 3.00 and 2.66 (bs, each 1 H, the bridgehead protons), 2.30 1.35 (complex, 4 H, bridge protons and CH2 ß to the vinyl group).…”