4. Acquisition

Time requirement: 0.5 h Sample: 3% strychnine in CDCl₃.

Record normal ¹H and ¹³C NMR spectra of the sample and optimize the spectral widths. Change to the 2D mode of the spectrometer and load the gs-HMQC pulse program. You have to set:

td2: 1 k data points in F2 td1: 256 data points in F, sw2: 10 ppm swl: 165 ppm offset of ¹H frequency: middle of ¹H NMR spectrum offset of ¹³C frequency: middle of ¹³C NMR spectrum p1: 90° ¹H transmitter pulse p2: 180° ¹H transmitter pulse p3, p4, p5: 90° ¹³C decoupler pulse dl:2s d2: 1/[2(C,H)] = 3.57 ms, calculated from 'J(C,H) = 140 Hz d3: 1/[2(C,H)] = 60 ms, calculated from "J(C,H) = 8 Hz start increment for ¢, evolution: 3 μs increment for f, evolution: 1/[2-sw1]} g1, g2, g3: sinusoidal-shaped field gradients with 5% truncation, 2 ms dura- tion and ca. 0.1 T/m strength, with gradient loop counters, ring-down delays (100 μs), lock blanking and gradient coil blanking switches according to actual instrumentation used. Gradient strength ratio: 5 : 3 : 4

5. Processing

Apply zero-filling in F, to 512 words in order to have a matrix of 512x512 real data points. Before Fourier transformation use an exponential window in F2 with lb = 5 Hz and 7/3-shifted squared sine window in F;. Phase correction is unnecessary, since the spectrum is displayed in the magnitude mode.

6. Result

The figure shows the 2D spectrum obtained on an AMX-500 spectrometer with an inverse multinuclear z-gradient probe-head and a BGU (10 A) gradient unit. Note the wealth of information obtainable from 2/(C,H) and °J(C,H) couplings in this molecule.