These compounds all have molecular formula C6H12O. Would you agree that their names are:
.......1. hexan-2-one ............................2. hexan-3-one ............................3. hexan-4-one
.......4. 3-methylpentan-2-one ............................................6. 4-methylpentan-2-one
.......................................5. 3,3-dimethylbutan-2-one...................................... 7. 2-methylpentan-3-one
Actually, compound number 3 is incorrectly named. It is in fact the same as compound number 2.
The counting of the carbon atoms should start at the end nearest the =O.
