Sample: 20% ethyl crotonate in CDCl.

Record normal ¹³C and ¹H NMR spectra and optimize the spectral widths. C hange to the 2D mode of the spectrometer software and load the pulse program for X,H- correlation. You have to set:

td2: | k data points in F2 tdl: 128 data points in F; sw2: 175 ppm swl: 8 ppm o1: middle of ¹³C NMR spectrum o2: middle of ¹H NMR spectrum p1, p2: 90° ¹H decoupler pulse p3: 180° ¹³C transmitter pulse p4: 90° ¹³C transmitter pulse dl:2s d2: 1/[2(C,H)] = 50 ms, calculated from "J(C,H) = 10 Hz d3: 1/[³J(C,H)] = 33 ms, calculated from "J(C,H) = 10 Hz initial value for t; evolution: 3 js increment for ¢, evolution = 1/[2-sw1] decoupler attenuation and 90° pulse for CPD ds: 2

5. Processing

Apply zero-filling in F, to 256 real data points. Use squared 7/2-shifted sinusoidal windows in both dimensions. Apply complex Fourier transformation corresponding to the N-type signal selection using the quadrature-off mode in F;. Phase correction is not necessary, since the data are processed in magnitude mode.

6. Result

The figure shows the 2D spectrum obtained on an ARX-200 spectrometer. Most of the cross-signals corresponding to '(C,H) can still be observed. Features of interest are the weak cross-signals of H-5, H-3, and H-2 to the carboxyl ¹³C nucleus C-1, and the large intensity difference between the cross-signals of H-4 to C-2 and C-3. Note, however, that the noise is considerably greater than that obtained for 'J(C,H) in Experiment 10.10, and that there is some breakthrough of axial signals.

7. Comments

The product operator description of the experiment is given in Experiment 10.10. The selection of delays d2 and d3 is frequently difficult, and is discussed extensively in the