[Osel]

I've been searching high and low for the past two days for a publication which used isotopic labelling to show which oxygen of a peracid is trasferred to an alkene to make an epoxide.

Something like this

RCOOO*H + RC=CR -> R-C(O*)C-R  (this is supposed to be an epoxide)

where (*) is the isotopic label, most likely O18.  

I can't find it for the life of me!!  If anyone has any suggestions, please please tell me!

Thank you

[movies]

I think that ¹⁸O labeled peracids are hard to make.  None shows up on a quick Beilstein search.  I would suspect that they could isomerize.

I think that it is pretty well accepted that the oxygen connected to the hydrogen in the peracid is the one that is transferred though.  Calculations support that.

[Osel]

Thanks a lot. I thought that much... This question was given without any explanations - this publication may not exist, for all I know.  I tried to come up with a route to make such a labelled peracid.  I know that ¹⁸O-labelled peroxide can be made from ¹⁸O₂, but reacting it with an acid anhydride would most likely give you a doubly labelled peracid (I haven't found the mechanism).  

[movies]

I looked for ¹⁸O labelled epoxides and it seems that they are usually made from labeled water or labeled oxygen gas.