[rjb]

Its been a long time since I posted on this forum, but here goes!

Ultimately, I am trying to get my head around what is going on at the interface between polar and non-polar liquids and I guess what I'm asking is a bit of a thought experiment rather than an attempt to achieve anything of practical value.

1. Imagine a situation where we have an immiscible pair of liquids such as Olive Oil (which I believe contains a small amount of free fatty acids - for the sake of argument Oleic acid) and say Deuterium Oxide. There is obviously a clear interface between the 2 liquids and they don't mix. The questions is, do the deuterium atoms in the D2O remain solely within the D2O layer, or can we expect them to migrate (albeit slowly) across the interface between the 2 liquids to some extent and end up in our Olive oil layer having exchanged with the Hydrogen atoms of the COOH group of Oleic acid?

2. Is anyone able to suggest some additional reading to help me understand what is going on at the molecular level at this kind of interface please? Obviously what we see is a lovely static interface, but I suspect there is all sorts of tumult and interesting stuff going on at a molecular level (and beyond all of the usual stuff relating to partition coefficient and liquid liquid extraction I vaguely recall from my undergraduate days) I know little to nothing about this and would really like to!

Kind regards

R

[rolnor]

Yes, I agree with you, it will be a slow exchange. Why do you want to know this?

[hollytara]

It's pretty complicated.... 

First, the solubility of the water in the olive oil and vice versa are not zero.  So there will be some D2O in the olive oil and this will rapidly exchange with any free oleic acid CO2H groups.

Second, the interface will not necessarily have the same composition as the bulk.  Would you expect the olive oil side to be enriched or depleted in oleic acid?

There is a lot of literature on this, and some beautiful simulations if you believe them.