Compensating for variation in 1JCH coupling constants in HSQC spectra acquired on small organic molecules

The HSQC sequence provides a sensitive way of determining the C-13 chemical shift of protonated carbons. It uses INEPT elements for magnetization transfer, which can only be optimized for one value of (1)J(CH), but small organic molecules contain a wide range of (1)J(CH) values. One popular method of compensating for (1)J(CH) variation is to incorporate adiabatic pulses into the INEPT elements. This article shows that this method fails for a significant subset of functional groups. It also shows that the effects of this failure can be reduced by avoiding refocusing delays and by using a J-compensated excitation element. Copyright (C) 2010 John Wiley & Sons, Ltd.