HSQC Heteronuclear single quantum

HC HMQC (heteronuclear multiple quantum coherence) and HC HSQC (heteronuclear single quantum coherence) are the acronyms of the pulse sequences used for inverse carbon-proton shift correlations. These sensitive inverse experiments detect one-bond carbon-proton connectivities within some minutes instead of some hours as required for CH COSY as demonstrated by an HC HSQC experiment with a-pinene in Fig. 2.15. 

HSQC Heteronuclear single quantum coherence, e.g. inverse CH correlation via one-bond coupling providing the same result as HMQC but using an alternative pulse sequence... 

Exploitation of the TROSY effect is rather straightforward. In contrast to 15N-HSQC (Heteronuclear Single Quantum Coherence) or standard triple-resonance experiments based on 15N-HSQC, no radio frequency pulses or composite pulse decoupling should be applied on amide protons when HN spin is not in the transverse plane. Likewise the 15N decoupling should be... 

A sequence suitable for measurement of J(H, P) and J(C, P) couplings is shown in Fig. 7.9a. The pulse sequence is a constant-time [13C, H]-HSQC (heteronuclear single-quantum correlation), in which 31P decoupling is applied in ot, in the first experiment and in co2 in the second. 

The HSQC (Heteronuclear Single Quantum Coherence) experiment is another widely used inverse detection experiment. It provides essentially the same information as HMQC, but relies on a different sequence of pulses to effect the transfer of magnetization between H and the heteronucleus. A direct comparison of HMQC and HSQC in the study of a natural product has indicated some advantages of the latter-sequence, which may provide improved sensitivity and narrower crosspeaks for improved resolution. ... 

The final step in the assignment of all resonances is correlating the C peaks with the proton peaks. This can often be done from chemical shift alone for the anomeric resonances, but not for other ring atoms. The most important pulse sequence here is HSQC (Heteronuclear Single Quantum Correlation), which involves six pulses to protons and four to C. The spectrum is now a non-symmetrical map with a peak at each carbon attached to a proton the projection on the C axis is the C DEPT spectrum and on the proton axis the ordinary proton spectrum (Figure 4.18). 

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