Deuterium labeling signal

However, NMR spectrometers use deuterium signals from deuterium-labelled molecules to keep them stable such substances are known as lock substances and are generally used in the form of solvents, the most common being deuterochloroform CDC13. 

Shifts due to either a- or (3-deuterium substitution are also quite significant, usually leading to well resolved fluorine signals for the deu-terated and undeuterated species, which can be useful in characterization of deuterium labeled fluorinated compounds. An example of the a-effect is shown in Figure 2.11, which depicts the fluorine NMR spectrum of F—CH2CH2CH2CH2CH2CD2—F, a molecule that has... 

The mass spectrum of cyclohexanone has been examined by deuterium-labeling to reveal the mechanism effective for propyl loss, [M-43], m/z 55, from the molecular ion, = 98. [38,39] The corresponding signal represents the base peak of the spectrum (Fig. 6.11). Obviously, one deuterium atom is incorporated in the fragment ion that is shifted to m/z 56 in case of the [2,2,6,6-D4]isotopomer. These findings are consistent with a three-step mechanism for propyl loss, i.e., with a double a-cleavage and an intermediate 1,5-H shift. 

Although you would expect deuterium (D) NMR to be every bit as useful as NMR, it is not carried out routinely as deuterium has a natural abundance of 0.015% and very low sensitivity. Furthermore, as the spin is greater than %, it is a quadrupolar nucleus and the signals are usually broad. Deuterium shows signals in the same chemical shift range as H (5 0-12), and NMR is most often used in experiments using D-labelled compounds to investigate reaction mechanisms. 

The signal assignments of the parent compounds 5 a- and 5 /i-androstane, 5 a- and 5 /i-pregnane and estrane [564] were performed by comparing the spectra with closely related derivatives, using substituent effects, off-resonance decoupled spectra and specifically deuterium-labeled analogues [564], The influence of different structural environments on the 13C chemical shift of the carbonyl carbon in keto steroids is illustrated by the values given in Table 5.10 [566]. The carbonyl carbon atom frequency in cyclopen-tanone moieties is shifted about 5 ppm downfield relative to that in cyclohexanone... 

Using the deuterium-labeled purine, the disappearance of the isotope at C-8 when in the presence of water is monitored by noting the corresponding increase in height (or area) of the signal due to the 8-proton. ... 

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