@Vidya...thanks for your reply. I have looked at that link and don't find the explanation very satisfying. I am familiar with Jim Clark's website and generally as you say it is full of great explanations but in this case it seems less than rigorous.
If the H ion is displaced from the ethanol in the way he describes then it must go somewhere. Jim's explanation is that it gets lost somewhere in the mixture. Well that's not very satisfactory. It surely must still exist either attached to deuterium oxide as an acidic ion or to form HDO as a neutral molecule or to exchange with two D atoms and form H2
O. If there was enough hydrogen in the original OH groups present in the sample to give a resonance on the NMR spectrum then when that hydrogen is displaced (where ever it goes to) there should surely be enough to produce a resonance at some other chemical shift value, to say it just disappears is not an explanation that I find acceptable. To say it appears somewhere else on the spectrum (for example as water) would make sense to me but to just disappear doesn't. I appreciate that deuterium does not normally appear as a peak in spite of having integer spin but that is because it has such a different chemical shift . So at this point I feel no wiser as to why the displaced hydrogen simply disappears from the spectrum. However it may well be that I am misunderstanding something ...I often do