[xshadow]

Hi...If I have  an asymmetric ketons (where one C-alpha  is secondary and the other one is primary) which product(s) I'll get when reacts with :

A) 1 mol Br₂
B) 2+ mol Br₂

In acid and basic condition
My textbook daesn't say much (actually NOTHING)about selectivity of this reaction

For acidic condition  and 1 mol Br₂ perhaps I'll get the most substitued  product beacuse in the mechanism  of resction I'll pass through a  more substituted alkenes (better stability).??
For 2 mol Br₂ I don't know if the second Br attacks the other alpha carbon or the same as before

Thanks!!

[kriggy]

What base are you using?

[xshadow]

What base are you using?

For basic condition I suppose Na+ OH-
Looking at the mechanism  in basic condition I see that in the first step I'll get a carbanion...now a carbanion with less  alkyl groups-R  is much more stable...so ,perhaps, in basic condition I'll get the keto-halide less substitued?
EDIT:  but with resonance iI'll get the enolate ion....so an alkene (so  +R groups  on Cps2  ,+ stability....so again ,the more substitued?)
Which is the correct one?

[kriggy]

Please draw the structures in some software or on paper and upload a picture (rotated correctly please) its quite hard to orient in organic chemistry described by words isntead of schemes.

Also the product of the reaction really depends on exact conditions, especialy the base and temperature being used, I can see getting different products in:
a) OH- + Br2, low temp
b) LDA + Br2, low temp
c) NaH + Br2, room temp

Its not really my cup of tea but I dont think less substitued enolate is more stable.

[spirochete]

Most Sophomore texts don't give examples of selectivity. I believe several examples of selectivity are nicely discussed in Clayden, Warren, Greeves second edition textbook. You should check there if you're interested.

[Babcock_Hall]

IIRC Jerry March's book has some comments about selectivity.  I am pretty certain that his book discusses di- and tri-halogenation under basic conditions, which is a slightly different topic.