I was wondering how the exchange of hydrogen by deuterium, like on arenes like benzene
could be monitored for a reaction on a scale larger than say 10 g of product. While I know that C6D6 is commercially available, used for NMR spectroscopy, I recognize
the observable signal of the protons bound to carbon is attenuated by the advancement of the reaction, and
the very deuterium installed equally serves as lock signal for the 1H-NMR spectrometer (similar to the deuterium in CDCl3). So there might be an experimental problem, from the spectrometer, too.
But what is a typical standard compound may serve as an added inner standard in such a reaction, provided protocols accessed so far mention extended heating / autoclave or/and presence some hydrogen gas to initiate the reaction as reaction conditions? Do commercial suppliers carry out the exchange hydrogen by deuterium, and (perhaps by virtue of even larger batches) obtain the 99%+ isotopically enriched product by sophisticated distillation / zone melting, recycling the partially deuterated product?