4. Acquisition

Time requirement: 40 min 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 HSQC pulse program and, if required, change the spectrometer to the inverse set-up. You have to set:

td2: 1k 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, p5: 90° ¹H transmitter pulse p2, p4, p6: 180° ¹H transmitter pulse p8, p9: 90° ¹³C decoupler pulse p7, p10: 180° ¹³C decoupler pulse dl:2s d2: 1/[4/(C,H)] = 1.72 ms, calculated from '(C,H) = 145 Hz initial increment for f,; evolution: 3 pas increment for f, evolution: 1/[4-sw1]

5. Processing

Apply zero-filling in F' to 256 real data points to obtain a matrix of 512256 real data points. Use exponential windows in both dimensions. Apply real Fourier transformation corresponding to the TPPI-mode signal selection using the quadrature mode in F}. Phase correction in both dimensions is necessary.

6. Result

The figure shows the HSQC spectrum obtained on an ARX-200 spectrometer with a normal forward dual probe-head. This demonstrates that a special inverse probe-head is not an absolute necessity. Note that the spectrum displays doublets in F, with the '(C,H) spin coupling constant and, in addition, the homonuclear splittings caused by H,H spin couplings. There is considerable breakthrough of signals from the protons bonded to ¹³C since no additional filter was used.