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Optimum conditions for high resolution 13C n.m.r. of coal- and oil-derived products

✍ Scribed by Herbert Dreeskamp; Heinz Kluge

Publisher
Elsevier Science
Year
1985
Tongue
English
Weight
811 KB
Volume
64
Category
Article
ISSN
0016-2361

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✦ Synopsis

Factors affecting the spin-lattice relaxation times T, of 13C resonances at 62.9 MHz were investigated for simplemixtures of tetralin, ethylbenzene, pentane and phenol and the prominent resonances of an anthracene oil and a coal-derived hydrogenation oil. Parameters varied were solvent temperature and nature--Cr(acac),, Cr(dpm),, Cr(hfac),, Fe(acac),, Fe(dpm),--and concentration of a paramagnetic relaxation agent (PARR). Effects of PARRs on relaxation rates are strongly dependent on neighbouring acidic or basic centres, but are much more uniform for Cr(hfac), than for Cr(acac),. The presence of basic or acidic compounds does not significantly affect the relaxation of ' % of the neutral components. Optimum experimental conditions are characterized by nearly uniform T, values of all resonances to be detected. While 2D spectra allow disentanglement of overlapping lines, choosing optimum conditions for the neutral constituents may lead to a loss of signals from the acidic or basic compounds.

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