1. Purpose

The disadvantage of the basic INEPT technique is the distortion of the multiplets. By adding a refocusing period with a subsequent additional purging pulse the extended version INEPT+ was developed, which yields coupled, polarization-enhanced NMR spectra of X nuclei with correct intensities within the multiplets. Furthermore, the sequence can be tailored to give a different phase for CH₂ groups with respect to the signals of CH and CH₃ groups, providing multiplicity information as described here for ethyl crotonate.

2. Literature

G. A. Morris, R. Freeman, J. Am. Chem. Soc. 1979, 101, 760–762.
D. P. Burum, R. R. Ernst, J. Magn. Reson. 1980, 39, 163–168.
O. W. Sørensen, R. R. Ernst, J. Magn. Reson. 1983, 51, 477–489.

3. Pulse Scheme and Phase Cycle

INEPT+ sequence with additional refocusing and purging pulses

4. Acquisition

Time requirement: 10 min

Sample: 20% ethyl crotonate in CDCl₃.

Load standard ¹³C NMR parameters and the INEPT+ pulse program. You have to set:

td	64 k
sw	200 ppm
o1	middle of ¹³C NMR spectrum
o2	middle of ¹H NMR spectrum