I'm a little confused by Destroyers road map #1 in Q118. It says that Cl2/H3O+ will add Cl to cyclohexanone ortho position.. why? Isn't a keto group meta directing? Or does that only apply to benzene addition?
I think it is only on a benzene ring. I think that Cl2/H3O+ will remove an alpha hydrogen and add a Cl. If you had a strong base with Cl2 I think it will also take off an alpha hydrogen and would add a Cl.
to the OP..the alpha proton (one on the carbon next to the carbonyl) is the most acidic proton. This proton is replaced with a Cl, Br, or whatever halogen. If it is an acid..it adds once (unless xs is used). If it's Br2 and OH- you should expect multiple halogens on the neighboring alpha carbons.
You were thinking of an aromatic ring. That's when those rules apply. For A.rings you would do, Br2 and FeBr3 (or any lewis acid) and you would get the meta electrophilic substitution. This is aromatic rings only. So the 4n+2 rule applies.