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240 220 200 180 160 140 120 100 80 60 40 20 0 ppm

240 220 200 180 160 140 120 100 80 60 40 20 0 ppm

CH2 carbon (position b, CH2OH). The peak at 50 ppm is the only peak in the DEPT-90 spectrum, so it can be assigned to the CH carbon (position c) in the molecule. The two most upfield peaks are positive in the DEPT-135 and missing in the DEPT-90, so they must be the two CH3 carbons (positions d and e in the structure). Note that the DEPT-135 is similar to an APT spectrum (Chapter 6, Fig. 6.16): there is an alternation of sign as we go from CH (positive) to CH2 (negative) to CH3 (positive). But in the APT spectrum, we would also see the carbonyl carbon peak (negative) and the solvent resonance (CDCl3, negative), and the sensitivity would be worse than that of a 13 C spectrum (which has about one-fourth of the sensitivity of DEPT) because there is no coherence transfer involved.

The width of the final 1H pulse in the DEPT sequence (©) affects the intensity and phase (positive or negative) of the 13 C peaks in a way very similar to the length of the refocusing delay A in refocused INEPT, according to the relation © = nJA. The intensities are shown below for the three types of carbon in DEPT:

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