shifts were externally referenced to the methyl resonance of hexamethylbenzeneat 17.36 ppm. Spectra were integrated across fourchemical shift ranges that were assigned to different C types asfollows: 185–165 ppm (carbonyl C), 165–110 ppm (aryl C), 110–45 ppm (O-alkyl C) and 45–0 ppm (alkyl C). Signal in spinning sidebands(SSBs) for the carbonyl and aryl resonances, which was <10%of signal in the corresponding central bands, was corrected for byadding twice the integrated signal of the low-field SSB to the integratedsignal for the central band, and subtracting this signal fromthe region where the corresponding high-field SSB falls (Schmidtet al., 1999; Gelinas et al., 2001), as indicated in Table 1
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