Sample: 5% ethyl! crotonate in CDCl₃ Record normal 1D ¹H and ¹³C NMR spectra, optimize the spectral widths and note the offsets. Switch to the 2D mode of the spectrometer software, load the pulse program and, if required, change the spectrometer to the inverse configuration. For the experiment you have to determine the 90° ¹³C pulse for GARP decoupling (see Exp. 2.5). You have to set:

td2: | k data points in F, tdl: 128 data points in F;

sw2: 8 ppm swl: 175 ppm offset of ¹H frequency: middle of ¹H NMR spectrum offset of ¹³C frequency: middle of ¹³C NMR spectrum p1, p3, p4: 90° ¹H transmitter pulse p2, p5: 180° ¹H transmitter pulse p7, p8, p9: 90° ¹³C decoupler pulse p6: 180° ¹³C decoupler pulse dl: 1s d2: 1/{2/(C,H)] = 3.5 ms, calculated from '(C,H) = 145 Hz d3: BIRD delay to be optimized for minimum FID, ca. | s; observe the incom- ing FID in the set-up mode and adjust d3 for minimum intensity (see Exp.

6.14). initial value for ¢; evolution: 3 jis increment for ¢, evolution: 1/[4-sw1] ¹³C decoupler attenuation and 90° pulse width for GARP ds: 2

5. Processing

Apply zero-filling in F; to 256 real data points to obtain a matrix of 512x256 real points. Use exponential or Gaussian windows in both dimensions. Apply real Fourier transformation corresponding to the TPPlI-type signal selection using the quadrature mode in F;. Phase correction is required; it is often sufficient to correct the phase only

6. Result

The figure shows the HMQC spectrum obtained on an ARX-200 spectrometer with a normal dual probe-head. This demonstrates that special inverse probe-heads are not an absolute necessity. Note that the spectrum displays only singlets in F2, which are further split by the homonuclear spin couplings. These also broaden the signals in the F; dimension. The breakthrough of the signals from protons bonded to ¹³C is dramatically reduced in comparison with Experiment 10.13.