Its time to revive my thread once again with another basic question. I almost made a new thread asking this, until I remembered I had made this thread for these type purposes.
Question: What is the mechanism of the safrole + KOH ---> isosafrole reaction?
I am uncertain how it proceeds, and am curious why this occurs.
I imagine that the base -OH removes a proton from the alkene in the first step, forming an intermediate carbanion. I am *guessing* that the formed carbanion would be in the isopropyl position, because it would be the most stable, as it has the least protons/is the most substituted?
If this happens, yay, "go me" but what happens next is beyond me. Logically some sort of electronic rearrangement would take place, but I am unsure just what happens. Carbanions are not prone to rearrangement like carbocations are, so I don't know why or where any formed carbanion would move to, and what effect this would have on the double bond.
Formation of an isopropyl carbanion wouldn't even affect the alkene, it would just turn R-CH2-CH=CH2 into R-CH2-C(-)=CH2, right? Hmm, I wonder:
This intermediate, if *somehow* could get an electron onto that terminal carbon (I have no idea how, so don't ask) then the double bond would be reduced to a terminal carbanion, and a radical at the isopropyl position, along with the isopropyl carbanion, and that radical might rearrange to a benzyl radical. The isopropyl carbanion could give up its electron, which would also form an intermediate radical, and of course two radicals means bond strengthening, restoring the alkenyl bond in a different location: The benzyllic position that corresponds to isosafrole.
Then the terminal carbanion would react with the water produced in the first step to steal back a proton and regenerate the hydroxide catalyst.
Am I close? Not even? What happens? If I am close, where does this mystery electron come from? It can't come from any sodium atoms because they are all already existing as Na+ and won't yield any more electrons.....
How does this isomerization work? Help please? I'm not asking for pictures in ISIS or anything, just a word description like I have given, and maybe an explanation using the "R-CH2-CH=CH2" diagrams I use.
Any help would be appreciated. Thanks.
PrimoPyro
Firm supporter of the "Purge The Couch!" movement. Vote for the purge today.