[cseil]

Hello,

I need to identify protons which could give secondary isotope effect in a certain reaction mechanism. Now, my question is: can I have a β secondary isotope effect if the proton is not on a carbon, but on an oxygen atom?

Something like H-O-(REACTION CENTER).

I have a rehybridization from sp3 to sp2 in the reaction center, so I was wondering if the proton attached to O would give secondary isotope effect, or not.

If the question is not clear, please let me know and I will upload an example.

Thank you!

Alessandro

[Babcock_Hall]

I see no reason why it is impossible to have a secondary isotope effect of the kind that you have described.  Offhand, I don't know of any examples however.  How could one measure this?

[cseil]

I see no reason why it is impossible to have a secondary isotope effect of the kind that you have described.  Offhand, I don't know of any examples however.  How could one measure this?

Hello, thank you for your answer.

To be honest, I do not know how to measure this practically. In fact, my question is only theoretical. Basically, in a paper the authors said they didn't consider secondary isotope effects, but I wanted to check which protons could have been responsible for this.

A situation like this:

H-O-C-C which becomes H-O-C=C

is perfectly acceptable, then.

Thank you.

[Babcock_Hall]

http://pubs.acs.org/doi/pdf/10.1021/bi00562a023

Here is an early paper that measures a few enzymatic β-secondary isotope effects, from one of the labs that pioneered such work.  There is some discussion of nonenzymatic effects.  Quite a bit of work has gone on in the interim.