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

td2: 1 k data points in F, 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)] = 3.45 ms, calculated from 'J(C,H) = 145 Hz d3: 1/[3(C,H)] = 2.29 ms, calculated from 'J(C,H) = 145 Hz initial value for ¢; evolution: 3 μs increment for ¢,; evolution = 1/[2-sw1] decoupler attenuation and 90° pulse for CPD

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. Note that the C,H spin coupling is removed in both dimensions. This is achieved by CPD decoupling in F, and by the 180° ¹³C pulse in the case of F).

7. Comments

The first proton pulse creates –/ Hy magnetization, which subsequently develops ¹H chemical shift during 1, as shown in Equation (1). The 180° ¹³C pulse p3 in the middle of ¢; removes heteronuclear spin coupling during f).

Hy tly, ly, > -ly y > JH, sin Qyt “Thy cos Qyhy ql) C,H spin coupling evolves during the delay r= d2, leading to an antiphase magnetiza- tion of proton with respect to carbon, as indicated in Equation (2). If the delay ris set equal to d2 = 1/2.(C,H) the corresponding cosine terms become zero.