Inverse Heteronuclear 2D Experiments HSQC, HMQC, and HMBC

INVERSE HETERONUCLEAR 2D EXPERIMENTS HSQC, HMQC, AND HMBC 

NMR Spectroscopy Explained Simplified Theory, Applications and Examples for Organic Chemistry and Structural Biology, by Neil E Jacobsen Copyright 2007 John Wiley Sons, Inc. 

Another advantage of ll observation is that a proton can only be attached to one 13C. We saw in Chapter 7 the complexities of refocusing of 13 C antiphase coherence different times are optimal for CH, CH2, and CH3 groups. A proton coupled to 13C will always be a doublet—never a triplet or quartet—and will evolve into antiphase or refocus from antiphase to in-phase in a time of exactly 1/(2J). 

We saw in Chapter 2 (Fig. 2.18) that the intensities of these two peaks (singlet for H-12C and doublet for H- C) are reversed for 13C-labeled compounds The wide doublet dominates, and the residual 12C shows up as a tiny central singlet. Not only are the protons directly attached to 13 C split into doublets, but also those two or three bonds away (13C-CH and 

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