Nondeuterated compound

Isotope Effects. If the hydrogen ion departs before the arrival of the electrophile (SeI mechanism) or if the arrival and departure are simultaneous, there should be a substantial isotope effect (i.e., deuterated substrates should undergo substitution more slowly than nondeuterated compounds) because, in each case, the C—H bond is broken in the rate-determining step. However, in the arenium ion mechanism, the C—H bond is not broken in the rate-... 

The intermediate 43 can be isolated. If a mixture of H2 and D2 is used, the product contains only dideuterated and nondeuterated compounds no monodeuterated products are found, indicating that (unlike the case of heterogeneous catalysis) H2 or D2 has been added to one alkene molecule and that no exchange takes place. ° Although conversion of 44 to the products takes place in two steps,the addition of H2 to the double bond is syn. 

This shows clearly that it can be very misleading to measure deuterated compounds in a nondeuterated solvent and to draw conclusions as to the behavior of nondeuterated compounds. 

None of the LC-MS experiments, under deuterated or nondeuterated conditions, provided a means for distinguishing hydroxylamine A-OH-DL from 1-pyridine-A-oxide-DL, and therefore these compounds were further investigated by LC-MS/MS. 

The following table lists the residual peaks that are observed in the H NMR spectra of common deuterated organic solvents. These peaks are generally attributed to the nondeuterated parent compound that serves as an impurity and are marked with an asterisk. In addition, other less significant peaks often arise due to other impurities. 

Lamos and colleagues reported the modification of cyclophilin A (CypA) by binding immunosuppressive cyclosporin A with a benzophenone-Dj j and a biotin moiety (compound 89, Fig. 11a) [91]. As a proof of principle, they used a 1 1 mixture of this TIP and its nondeuterated isoster for the selective PAL and pulldown of CypA among three other proteins. Subsequent tryptic digestion of the elutes and LC-MS/MS analysis allowed the identification of 11 CypA characteristic peptides, two of which were modified with the probe, as evidenced from the double, 11 Da separated, peaks in the mass spectra. The large 11-Da mass difference allowed easy visual recognition of labeled peptides in the mass spectra, which makes this a powerful method for determination of the modification site after PAL however, application in more complex systems still remains to be done. 

The appropriate C6D5 deuterated isotopomers of 28, 29 and 32 were also studied. C—D carbons in the deuterated isopotomers behave in dipolar dephased spectra as quaternary carbons and the changes in spectral patterns of nondeuterated and pentadeuterated compounds were used for 13C chemical shift assignment. The spectra of 28, 30, 31 and 32 were also recorded at elevated temperature. It was found, contrary to Maciejewska s results,87 that in 28, 30 and 32 rotation of the aromatic rings is induced at elevated temperatures. 

Hydrogenation of homoproaporphines using Adams catalyst can result in racemization at C-6a. Thus reduction of the homoproaporphine 18 yielded diastereomers 19 and 20. However, when palladium was used as a catalyst, the substrate 18 provided the unepimerized ketone 21. In a parallel experiment, compound 18 deuterated at C-6a, also furnished the nondeuterated products 19 and 20. ... 

---