Figure 3.

Comparison between the common phenotypic NMR spectral interpretation using n+1 and 2ⁿ rules versus the theory-driven genotypic QMSA approach. The aromatic ¹H patterns of guaiacol (2; 500 MHz) exhibit severe overlap and higher-order effects. Both mislead traditional 1D/2D-based peak and δ assignments and result in ambiguous, wrong, or no coupling constants. The QMSA-driven genotypic approach provides a complete and accurate interpretation and encodes everything in just 13 variables: four chemical shifts, six J-couplings, one intensity, and two line shape descriptors (line width, Gaussian contribution). In contrast, phenotyping picks up to 33 peaks (depending on spectral resolution, field strength, acquisition, and processing/picking algorithms), each with position, intensity, and two line shape parameters, for a total of 132 variables. Phenotyping still cannot decode the molecular spin parameters, even at 1.2 GHz, as NMR spectra of 2 retain their higher order.