IUPAC naming rules

viciousp

1. The problem statement, all variables and given/known data
What is the IUPAC name for the following compound. (Benzene with two chlorines sticking out one at Carbon 2 the other at Carbon 5)


2. Relevant equations



3. The attempt at a solution
I understand that the compound's name has to be something like 2,5-dichlorobenzene but are the two numbers in front supposed to be 2 and 5 or is the supposed to be a different number.

viciousp

http://img355.imageshack.us/img355/7945/hexaneiz7.png

picture if you need it

symbolipoint

The way you describe, you might also say a chlorine is at carbon 1 and at carbon 2. My guess, if this numbering is acceptable, is "1,2-dichlorobenzene". An alternative name may actually be better accepted; this is the best I can do right now without re-reading from a textbook or checking a reference book.

chuck_

Eh, the above poster is a little off. IUPAC dictates you start at the closest carbon to the substituants. Cl in this case, so all you do is number the chlorines making sure that Cl is at carbon one, and (it doesn't apply in this situation) that any other substitutants would be in their lowest number.

the answer is 1,4-dichlorobenzene


a little more advanced - since this is a hexyl compound, you could name it ortho-dichlorobenzene because the first chloride dictates carbon 1, and the other is in the ortho (opposite) position. If it was adjacent (1,2) it would be para-, and if it was in between opposite and adjacent (1,3), it would be meta-.