Deuterium oxide, exchange with enols

It has been reported that exchange of protons activated by enolization can be performed directly in a glass inlet system of the mass spectrometer prior to analysis by heating the sample at about 200° with deuterium oxide vapor for a few minutes. " Exchange has been observed with 2-, 3-, 6-, 11- and 17-keto steroids, but the resulting isotopic purity is usually poor,... 

Sulfhydryl protons usually exchange at a low rate so that at room temperature they are coupled to protons on adjacent carbon atoms (7—8 Hz). They do not exchange rapidly with hydroxyl, carboxylic, or enolic protons on the same or on other molecules thus, separate peaks are seen. However, exchange is rapid enough that shaking the solution for a few minutes with deuterium oxide replaces sulfhydryl protons with deuterium. The absorption range for aliphatic sulfhydryl protons is 81.6 to 8 1.2 for aromatic sulfhydryl protons, 8 3.6 to 8 2.8. Concentration, solvent, and temperature affect the position within these ranges. 

For example, chemical analyses and measurements of the absorption spectra of 2,4-pentanedione, CH3COCH2COCH8 (acetylacetone), by Grossman and by Acly and French, indicate that the enol form is present in water at 25° to the extent of 15 to 20 per cent and in 95 per cent alcohol to the extent of 55.7 per cent. The tautomerism has also been studied by means of the Raman effect, by exchange reactions with deuterium, and by polarographic oxidation-reduction measurements. Insofar as 2,4-pentanedione and other 1,3-diketones exist in the enol form, they probably... 

---