[faust]

Hello.

This is a simple question : Are the radicals stable in THF?

Because I tried the following thing :

In THF : Iodocyclohexane (0.01M) + SmI2 (4 eq) + AcOEt (10eq).

After GC analysis : Iodocyclohexane is totaly consummed, but there are no product ! (may be volatil cyclohexane...)

So I wonder if the cyclohexyl radical could take an hydrogen from THF instead of getting further reduced to cyclohexyl anion by SmI2.

Thank you,

[miraculix]

Hello faust,

I'm doing radical chemistry as well (Titanocene-derived). Our standard solvent is THF, so Carbon-centered radicals should be fairly stable under these conditions.
But, taking into account, that the BDE for alpha-Hydrogen in THF is around 92 kcal/mol, the possibility of reduction should be possible in some cases. I unfortunately don't know too much about the kinetics in SmI2 mediated reactions, but if the second step (= generation of the anion) is slow, reduction of the carbon-centered radical might be a problem.

cheers

miraculix

[ziqquratu]

Radicals are generally quite stable in THF. In addition to miraculix's testimony, remember that the standard method for drying THF is to reflux it over sodium wire, with some benzophenone added. When the solvent is dry, the benzophenone forms a ketal radical, which is intensely blue (the solution is colourless when wet, since water reacts with and quenches the ketal, thus giving a visual indication of dryness!).

My guess is that, if radicals are likely in your reaction (like miraculix, I know nothing of the chemistry of Sm compounds), then it's possible that a similar thing is happening - that is, water is quenching your radicals to give plain cyclohexane. Are you sure your solvent was dry? Did you quench the reaction before running the GC?