I wouldn't unless there was some reason you did poorly and think you'll do better this time - sickness, etc. Just try to do better in orgo. I know someone addressed a situation like this previously in a different thread.
gll8889 is correct. Organic is more important than general chemistry in the eyes of adcoms. Forget it and concentrate on doing well on Orgo. Then make sure to explain why you got such a poor grade in gen. chem. in your personal statements and supplementals.
although getting higher grades in later courses will help, some colleges look at your pre-req gpa specifically and then overall, so make sure your prereq gpa is high enough.
A "C" won't stop you from getting into pharm schools, if the rest of your grades are stellar... Most schools just look at your overall and pre-req gpa, so that "C" grade most likely won't even be looked at.