1. Purpose

As in Experiment 4.14, this technique correlates an ¹H signal with ¹³C signals, but in this case the nuclei concerned are connected by two or three bonds. As such it is a 1D equivalent of the 2D COLOC technique (Exp. 10.12). Again, this experiment can be performed in the inverse mode either as a 1D or a 2D method (gs-SELINCOR, Exp. 11.13 and HMBC, Exp. 10.16). The main purpose of the educational experiment described here is to simplify proton-coupled carbon spectra, which can not only give assignment information but can make the analysis of the spin system much easier.

2. Literature

M. L. Martin, J.-J. Delpuech, G. J. Martin, Practical NMR Spectroscopy, Heyden, London, 1980, Ch. 6.
K. Bock, C. Pedersen, J. Magn. Reson. 1977, 25, 227–230.

3. Pulse Scheme and Phase Cycle

Carbon-13 acquisition with broad-band decoupling during the delay and low-power continuous-wave decoupling during acquisition

4. Acquisition

Time requirement: 15 min

Sample: 20% ethyl crotonate in CDCl₃.

Record a normal ¹H NMR spectrum and an ¹H-coupled ¹³C NMR spectrum (gated decoupling, see Exp. 4.11) of ethyl crotonate and note the ¹H frequency of the upfield