Kevin's Watch

Ok folks..its been 14 years since I took organic chemistry and almost as long since I used it....I am hoping some of our folks here might be able to help me out with this.....

I have a tertiary alcohol that undergoes some substitution reaction where the alcohol group is replaced with an aromatic ring......any ideas on mechanisms for this process or conditions required for it to occur?

conditions are probably reflux... It's always reflux...

Yeah I would think you could use reflux, but this phenomenon happened in real life on the surface of an automobile....not thinking you could fit a heating mantle around a car and that'd be one mean condensor :\

Seriously, I guess I'm looking for things like pH and metal catalysts to be involved with the process....you might get a reflux-like situation due to heating from the sun...

I only remember one thing from chemistry:

Johnny was a chemist
Johnny is no more
What Johnny thought was H2O
Was H2SO4!!

Creator wrote:I only remember one thing from chemistry:

Johnny was a chemist
Johnny is no more
What Johnny thought was H2O
Was H2SO4!!

LOL...I've never heard that one before!

Substitution of a tertiary alcohol?

A tertiary alcohol is an alcohol where the OH group is sitting on a carbon with carbonyl substituents on the last three positions right?

Just askin'. It's been a while for me to (organic chemisty of course )

I think that's right, Prebe.
I'm in the same situation - can't remember my A-level chemistry well enough to think of anything.

A tertiary alcohol is a carbon with three aliphatic groups attached to it and then one alcohol.

Aliphatic means a carbon chain of some random make-up that does not contain an aromatic.

I forwarded a link to this thread to Paul, in the hopes it would get him to post. He too is embarrassed to not remember enough, so he asked me to post this guess for him.

the only thing that comes to mind is that it's the aryl that undergoes the substitution, not the alcohol, and that the process might take place in the process of nickel...but there's nothing for me to base this on except my B+ ten years ago. :/

Ok....I have nickel present in some samples but not others. Does it have to be nickel or can it be any divalent metal? (yeah I know I'm pushing it but I'm really stuck here)

Forwarding question back to Paul. It might not be guessed at until tomorrow though.

Here's Paul's reply. I have no idea if it's any help though...

Crap. The key factor that I remember was that surface properties of nickel catalysts were particularly useful for aryl substitutions, but I can't recall whether the valence makes a difference. If pressed, I would hypothesize cupro-nickel alloys maybe, precious metals like platinum yes, alumina and ferrous metals no. Sorry about not being more specific.

On a related note, you would probably want to see whether the reaction was taking place at neutral or slightly basic pH to prevent competing esterification of the alcohol, and in conditions as dry as possible to prevent incomplete adsorption to the catalyst. Once again, this is mostly guesswork here.

Lorelei wrote: I have a tertiary alcohol that undergoes some substitution reaction where the alcohol group is replaced with an aromatic ring......any ideas on mechanisms for this process or conditions required for it to occur?

Sounds like an acid catalyzed reaction to me. Tri-substituted cations (like trimethylcarbenium) are stabilized relative to less substituted ones. The cation reacts with the aromatic compound by a standard electrophilic substitution reaction (see below).

Me3COH + H+ ---> Me3C+ + H2O
Me3C+ + PhH ----> Ph-CMe3 + H+

All I can recall about organic chemistry (it's been 24 years), is that my teacher was called Dr Webster and he was a sadistic bugger.

But he must have been good, because I got an A in both my O grade and Higher Chemistry.