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Determination of heteronuclear long‐range H,X coupling constants from gradient‐selected HMBC spectra
Author(s) -
Willker Wieland,
Leibfritz Dieter
Publication year - 1995
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1260330804
Subject(s) - heteronuclear molecule , chemistry , coupling constant , spectral line , range (aeronautics) , nuclear magnetic resonance , analytical chemistry (journal) , computational chemistry , nuclear magnetic resonance spectroscopy , stereochemistry , organic chemistry , physics , quantum mechanics , materials science , composite material
A gradient‐selected J ‐HMBC experiment is presented. Coherence selection with magnetic field gradients results in HMBC spectra in which t 1 noise is very low or completely eliminated. This makes it possible to detect unequivocally very small (<2 Hz) long‐range H,X coupling constants. With a slight modification, the HMBC experiment can be used for the quantitative measurement of these couplings. The signal amplitude of spectra with increasing coupling evolution time τ shows the characteristic sin (πJ XH τ) dependence. By fitting a sine curve to the experimental data or by performing a 3D J ‐resolved HMBC experiment, accurate n J XH coupling constants are obtained. This method is especially useful for estimating coupling constants between protons and unprotonated heteronuclei, e.g. quaternary carbons, 15 N nuclei in labelled prolines or 31 P in organophosphates.