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The carbon skeleton of a molecule can be determined by using the powerful 2D INADEQUATE experiment, but the method suffers from very poor sensitivity at natural carbon-13 abundance. A computer program, described previously, has been significantly improved in its ability to recognize AB spectral patterns corresponding to carbon-carbon bonds which makes it possible to evaluate reliably spectra with rms S/N ratio as low as 2.5, i.e., nearly 1 order of magnitude below the level required for routine manual interpretation. Application of the INADEQUATE experiment to samples containing as little as 20 mumol of a compound of interest is now possible. The method is described in detail and critically evaluated by means of examples and simulations.

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The perturbation-response behavior of various nuclear spin polarizations associated with methanol's 13CH3 spin grouping were examined in the vicinity of the T 1 minimum. Dipole−dipole auto- and cross-correlation spectral densities indicate unhindered methyl rotation about a triad axis oriented perpendicular to the principal axis of an axially symmetric reorienting molecular framework. This finding is consistent with a strongly associated solute (methanol)/solvent (glycerol) mixture. In the motional regime investigated, it is predicted that relaxation-induced polarization transfer is manifest in differential frequency shifts of various multiplet components. Indeed, this study clearly demonstrates reproducible second order spectral shifts. However, the theory developed in this work accounts for only a portion of the observed shifts.