I am analyzing some deuterated standards by HS/GC/MS as part of a process improvement study I am performing. One of those standards is cyclohexanone-d4. It is clear that as time in the HS oven increases the amount of cyclohexanone-d4 is decreasing, but the peak for cyclohexanone is proportionally increasing. Each vial has some polymeric material in it, and the conversion veries by material and also seem to catalyze it (standard in empty vial showsminimal conversion).
Since the deuterium atoms are on the cyclohexanone ring it is not clear to me how this may be occuring. Does anyone have any ideas or a similar expirience?
I attached a copy of an article that will help you.
The Catalytic Hydrogen Reduction and Deuterium Exchange of cyclopentanone on Evaporated Metal Films and Some Observations on cyclohexanone .
Professor Yehia Khalil, Yale University, USA
Fellow of the University of Oxford, UK
Do you know where on the ring the 4 deuteriums are located?
Keto-enol tautomerization could facilitate exchange the deuteriums, especially if all 4 were at the ortho positions.
https://www.quora.com/Which-has-more-enol-content-cyclohexanol-or-cyclohexanone
In fact in '65 an old packed GC column pretreated with D2 was used to deturate cyclohexanone (& others) via enolization (to permit MS ionization studies). Article Convenient Deuterium Labeling for Mass Spectrometry via Exch...
Enol formation might be aided if cyclohexanone concentrates on the polymers in the HS vial. Organic solvents and different H-bonding seem to allow higher enol formation Article A Theoretical Study of the Enol Contents of Cyclohexanone, C...
....and of-course, the increasing temperature of the oven crosses more activation energy barriers increasing the rate and number of mechanisms for exchange.
Actually they are all in the ortho position. I think your explanation makes sense so thanks for the suggestion.
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