General Appearance of Inverse 2D Spectra

2 GENERAL APPEARANCE OF INVERSE 2D SPECTRA 11.2.1 2D HETCOR versus 2D HSQC/HMQC 

We saw in Chapter 9 that the INEPT experiment can be extended to a 2D correlation 

Both experiments yield a 2D spectrum that has 13C chemical shifts on one axis and lH chemical shifts on the other axis, with crosspeaks representing the one-bond relationship between 13C and H. The main difference is that the HSQC spectrum has the 13C chemical shifts on the indirect (F ) axis whereas the HETCOR spectrum has the 13C chemical shifts in the directly detected (F2) dimension. Thus, an HSQC spectrum looks like a HETCOR spectrum turned on its side (90°). We saw in the last section the consequences of detecting the1H signal directly We have a much stronger signal (16 x) and better resolution (complex 

Between these pairs there will be a vertical streak (parallel to the F axis) that represents the 12C-bound proton signal. Because the 12C-bound proton signal is not modulated in t, the 13C evolution period, it has no F frequency, and so it just appears at all F frequencies that is, as a vertical streak. This problem can be solved by coherence pathway selection using phase cycling or gradients. 

2 One-Bond (HSQC/HMQC) Versus Multiple-Bond (HMBC) 2D Spectra 

---