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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: ABA2015 on October 09, 2014, 04:11:27 PM

Title: ph migration in baeyer villiger oxidation reaction!!
Post by: ABA2015 on October 09, 2014, 04:11:27 PM

hi all
as you know in baeyer villager reaction  the migratory aptitudes is  as follow
R3C+, R2HC+ , ph , R1H2C+ , CH3
I know that the most stable cation migrate but if it is so is ph a stable cation to migrate? I have found these explanation about migratory aptitudes but it doesn't clarified me why ph is a good migrating group :'(
http://classes.yale.edu/02-03/chem125a/125webSpring/BaeyerVilliger/migratoryaptitude.htm (http://classes.yale.edu/02-03/chem125a/125webSpring/BaeyerVilliger/migratoryaptitude.htm)
can you explain me?
thanks for your help

Title: Re: ph migration in baeyer villiger oxidation reaction!!
Post by: C-hemCards on October 10, 2014, 06:40:25 PM

Good question--the simplest answer is that the aromatic ring (the pi bond system) can help to partially stabilize the developing positive charge during the migration event. No doubt, the perfect orientation of the pi-cloud of electrons into the anti-bonding orbital of the O-O linkage also assists in the migration.

Title: Re: ph migration in baeyer villiger oxidation reaction!!
Post by: ABA2015 on October 12, 2014, 02:25:43 PM

Quote from: C-hemCards on October 10, 2014, 06:40:25 PM

the simplest answer is that the aromatic ring (the pi bond system) can help to partially stabilize the developing positive charge during the migration event. No doubt, the perfect orientation of the pi-cloud of electrons into the anti-bonding orbital of the O-O linkage also assists in the migration.

thanks for your reply, I think you are right just I can't understand how a phenyl ring can be a cation, because I guess the aromaticity must inhibit the positive charge on the ring, but if it had a alilic carbon it could accommodate the positive charge, am I right?

Title: Re: ph migration in baeyer villiger oxidation reaction!!
Post by: orgopete on October 12, 2014, 03:29:37 PM

Let me suggest that a different way to approach the question. What is being given is the actual order of migratory aptitude. What I would suggest is to actually write out the mechanism. I think if you do, the migrating groups may not be stabilizing cations (a phenyl group can). What is it about the groups that allow them to migrate? What are they actually doing electronically in the migration? When you do that, why might a phenyl group migrate better than a primary carbon, but worse than a secondary or tertiary?