Do you mean electrophilic acyl substitution? an acyl group contains an electron-deficient carbon, so it will be added electrophilically.
An example is the electrophilic aromatic (Friedel-Crafts) acylation of benzene; electrons from a double bond from benzene will attack the carbonyl acyl carbon in an acyl halide and the halide will eventually leave. But now you have a carbocation intermediate, which will then undergo elimination to reform the stable, aromatic ring (this will release a proton).
I haven't looked at the aamc outlines for o chem. But benzene substitutions (bromination, sulfonylation, alkylation, nitration, etc.) should be there, no?