ethyl methyl ketone = methyl ethyl ketone = MEK
check the stimulants forum (pill extractions etc)
No such thing as isobutyl ketone, afaik, however you may be talking about methyl isobutyl ketone (MIBK), I have not used MIBK since eighth grade, did a science project on thermofusion of PVC polymers to metals, and the primer formulation contained MIBK. Never used it since for anything else.
EDIT: Oops I did not see that methyl group inbetween your isobutyl, and your ketone. Isobutyl methyl ketone would be a synonym for MIBK AFAIK.