VII. 13C-{1H} NMR Spectra - I

This section gives you some useful information about ¹³C{¹H} NMR spectroscopy. Examples of spectra of 30% menthol in CDCl₃ taken on the Unity+300 and VXR-S 400 are given in Figures VII-1 and VII-2 respectively. Some of the important default ¹³C NMR acquisition parameter values are given below.

Unity+300	VXR-S 400
Spectrometer Frequency (sf) = 75.432 MHz	Spectrometer Frequency (sf) = 100.580 MHz
Spectral Width (sw) = 18,859 Hz	Spectral Width (sw) = 25000 Hz
Acquisition Time (at) = 0.820 sec	Acquisition Time (at) = 0.819 sec
Number of Points (np) = 30912	Number of Points (np) = 40960
Digital Resolution = 1.22 Hz	Digital Resolution = 1.22 Hz
Line Broadening = 1.00 Hz	Line Broadening = 1.00 Hz

The symbol ¹³C-{¹H} implies a ¹³C NMR spectrum where the ¹H nuclei are decoupled from the ¹³C nuclei. This is a double resonance experiment, just as described in section VI for homonuclear decoupling except that now the observed nucleus (¹³C) and decoupled nucleus (¹H) are not the same. This experiment is called heteronuclear decoupling, and is a 1PULSE experiment, as described in section II, with the addition of the decoupling field (Figure VII-3). It should be noted that the proton decoupling field is left on during the entire experiment.