Load standard ¹³C NMR parameters and the DEPTQ pulse program. You have to set:

decoupler attenuation for hard decoupler pulses [−3 dB]
td	64 k
sw	200 ppm
o1	middle of ¹³C NMR spectrum
o2	middle of ¹H NMR spectrum
p1	90° ¹H decoupler pulse [10.5 μs, −3 dB]
p2	180° ¹H decoupler pulse [21 μs, −3 dB]
p3	135° ¹H decoupler pulse [15.75 μs, −3 dB]
p4	90° ¹³C transmitter pulse [12.5 μs, 0 dB]
p5	180° ¹³C transmitter pulse [25 μs, 0 dB]
d1	1 s
d2	1/[2¹J(C,H)] = 3.5 ms, calculated from ¹J(C,H) = 145 Hz
decoupler attenuation and 90° pulse for CPD [17 dB, 100 μs]
ns	16
ds	2

5. Processing

Use standard 1D processing as described in Experiment 3.2. Adjust the phase for the methyl group signals positive.

6. Result

The figure shows the ¹³C DEPTQ spectrum of ethyl crotonate obtained on a DRX-400 spectrometer with a 5 mm multinuclear probe-head. Clearly, the carbonyl signal can be observed, whereas the signals of the proton-bearing carbon atoms are DEPT-polarized and display the usual sign change.

7. Comments

The product operator formalism for the proton-bearing carbon atoms is exactly as already described in Experiment 6.9 and will not be repeated here. The magnetization vector of the quaternary carbon atoms is moved to the −y axis by pulse p4, where it stays unaffected by the further pulses on the ¹³C channel, which are all from the x-direction. Thus, the signals of the quaternary carbon atoms are not canceled by the phase cycle as in the normal DEPT.

The method can be used for complete editing in a way quite similar as described in Experiment 6.10, but now for each setting of p3 (45°, 90° and 135°) two DEPTQ spectra must be recorded, with the phase of p4 set first to +y and then to −y. The exact recipe for a complete editing is given in the literature. Furthermore, there exists a variation (not shown) which includes a feature of APT, with the first pulse p4