Name the following compound:
Why would this be 5-ethyl-6,6-dimethyl-3-heptene when in alphabetical order it should be 6,6-dimethyl-5-ethyl-3-heptene?
The prefixes di-, tri-, etc. are not considered when determining the alphabetical order of the substituents. So the order is actually determined like this:
You can read up on this matter when following this Wikipedia link.