Analyses of Complex Mixtures by F₁ Homo‐Decoupled Diagonal Suppressed Total Correlation Spectroscopy

Abstract

A diagonal suppressed F decoupled total correlation spectroscopy(TOCSY) experiment is developed for analyses of complex mixtures. In 2D homonuclear correlation, assignment of the cross peaks is crucial for structure elucidation. However, when cross peaks are close to the diagonal peaks in overcrowded spectral regions, their assignment becomes tedious. In complex mixtures, the presence of multiple spectra along with broad and complex proton multiplets owing to homonuclear scalar couplings degrade the resolution to the extent that assignment of various cross peaks becomes tedious or impossible. Herein, a diagonal suppressed total correlation technique with F decoupling is presented to improve the resolution of the cross peaks. The resolution of the cross peaks is improved by both diagonal suppression as well as the collapse of the multiplets to singlets. Application of the method to a few mixtures of organic compounds reveals better identification of the cross peaks relative to other TOCSY variants.

Identification of metabolites in coriander seeds (Coriandrum Sativum L.) aided by ultrahigh resolution total correlation NMR spectroscopy

“…Broad multiplets can be converted to narrow singlets, via broadband homonuclear decoupling schemes, [26][27][28][29][30][31][32][33][34][35][36][37][38][39] or Keeler's projection-rotation, [39,40] which refocus the effect of 1 H-1 H scalar couplings. Such broadband homonuclear decoupling techniques include Zangger-Sterk-based TOCSY, [41] F 1 -PSYCHE-TOCSY, [42] and 13 C edited F 1 -BIRD-TOCSY [43] with diagonal suppression. In some situations where a narrow chemical shift region is to be studied, band-selective homodecoupling methods or homonuclear band selective [44,45] method is favorable.…”