W. C. Coburn

The 13C nuclear magnetic resonance spectra of some 2-, 6-, and 2,6-substituted purines

Abstract The 13 C NMR spectra of purine and 26 substituted purines are presented. In most cases, proton-coupled spectra as well as the decoupled spectra were obtained. Chemical shift assignments are reported, and one-bond and long-range coupling constants are given where measurable. Substituent effects on chemical shifts were investigated and shielding constants derived and found to be approximately additive. Correlations of δ c-8 with σ p + and of δ C−5 with σ R were found. Tautomerism of the labile proton between N-7 and N-9 is proposed as the cause of line broadening, particularly of the lines due to C-4 and C-5, in nearly half of the substituted purines studied.

The 1H and 13C nuclear magnetic resonance spectra of 2-aminoperimidine hydrobromide

Abstract The 1 H and 13 C NMR spectra of 2-aminoperimidine hydrobromide, an example of a little-studied N -heterocyclic ring system, have been determined in dimethyl sulfoxide solution. In this solvent, contrary to some previous reports in the literature, both spectra show that the base is protonated on the ring nitrogen, rather than on the amino group. Chemical shifts and some coupling constants are reported.

The 13C nuclear magnetic resonance spectrum of cis-2-isopropenyl-1-methylcyclobutaneethanol

Abstract The 13 C-NMR spectrum of neat cis -2-isopropenyl-1-methylcyclobutaneethanol, a component of the male sex pheromone of the boll weevil, is reported. Both chemical shifts and direct CH coupling constants are tabulated, and their values are compared with corresponding values for model compounds. The measurable long-range CH coupling constants are given.