I was reading about the effects of adding substituents in designing drugs and read that halogens, like methyl groups, make the molecule more lipophilic. Don't halogens would make molecules more polar since they are so electronegative? I thought halogens would make a molecule more hydrophilic and less lipophilic, how is it the other way around?
With regard to designing drugs, it likely depends on WHERE you add the halogen. Chances are, if it makes the molecule less polar, its because something polar is on the other end of the molecule already. Also, aren't halogens also often compared with methoxy
groups in terms of their ability to bind a receptor? Maybe there was just a typo.
You are correct in your reasoning, and in fact, just plain correct in general. Compare the "new freon" (1,1,1,2-tetrafluoroethane) with ethane to see a popular example of why you are right, although neither are called drugs (and its propane+isobutane that is a non-polar coolant, not ethane (too cold), but whatever)
...Then again, I guess if you choose to compare hexachloroethane with carbide anions, why by golly, I guess adding those halogens do make it less polar!
p.s. how is it that the firefox spell checker has the right spelling for the IUPAC name of new-freon, but lacks the ability to realize that "colour" is actually a correct spelling??