4. Acquisition

Time requirement: 10 min Sample: 3% strychnine in CDCl₃ Record normal ¹H and ¹³C NMR spectra of the sample and optimize the spectral widths for CH, signals. Change to the 2D mode of the spectrometer and load the gsHMQC pulse program. You have to set:

td2: 1 k data points in F, td1: 256 data points in F; sw2: 10 ppm swl: 165 ppm offset of | H 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: 90° ¹³C decoupler pulse d1:2s d2: 1/[2(C,H)] = 3.57 ms, calculated from 'J(C,H) = 140 Hz d3: set equal to d2 minus gradient duration start increment for ¢, evolution: 3 μs increment for ¢, 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 ¹³C decoupler attenuation and 90° pulse for GARP (19 dB, 70 μs) ns: 1

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 F, 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 that ¹³C nuclei with diastereotopic attached protons show two different correlation signals.