coupler pulse in the ¹³C channel. Change to the 2D mode of the spectrometer software. You have to set:

¹H transmitter attenuation and 90° pulse-width for broad-band presaturation [28 dB, 100 μs]
td2	2 k data points in F₂
td1	32 data points in F₁
sw2	1 ppm
sw1	45 Hz
o1	center of methyl group region in ¹H NMR spectrum
o2	on resonance of the olefinic carbon atom C-2 at δ_C = 123.6
p1	90° ¹H transmitter pulse
p2	180° ¹H transmitter pulse
p3	selective 90° ¹³C decoupler pulse, half-Gaussian shape (10 ms length at 66 dB)
p4	90° ¹³C decoupler pulse
d1	6 s
d2	1/[2J(C,H)] = 50 ms, calculated from ⁿJ(C,H) = 10 Hz
initial value for t₁ evolution: 3 μs
increment for t₁ evolution = 1/[2·sw1]
preacquisition delay: as small as possible
ds	4
ns	16

5. Processing

Apply zero-filling in F₂ and in F₁ to 2 k and 128 real data points respectively. Use unshifted sinusoidal windows in both dimensions. Apply complex Fourier transformation corresponding to the N-type signal selection using the quadrature-off mode in F₁. Phase correction is not necessary, since the data are processed in the magnitude mode.

6. Result

The figure shows the result obtained on an AMX-500 spectrometer, with the region of the methyl group attached to the olefinic carbon expanded. The ³J(C-2, H-4) spin coupling of 6.6 Hz can be seen in F₂, whereas the homonuclear couplings to the two olefinic protons are observed in F₁. This long-range C,H coupling constant can also be obtained by Experiment 7.10, using ¹³C rather than proton detection, and is then observed in the F₁ dimension. Note that some axial peak breakthrough at 0 Hz in F₁ is unavoidable; residual signals from protons bonded to ¹²C may also appear, but are outside the region of interest. Along the F₁ axis the normal signal of H-4 is shown.