Naming Multifunctional Organic Molecules

If you are naming molecules with multiple functional groups your first priority is to keep the numbers low and then when you write the name you put them in alphabetic order.

So for example this molecule...

...is called,  3-Chloro-1-Iodo butane

This is right because

- it keeps the numbers low (the alternative is "2-chloro-4-Iodo", i.e. 1,3 is lower than 2,4)

- and we have put it in alphabetic order

There is a more complicated rule that groups have different priority based on their Mr but you don't really need to know that,

The other fact it is worth knowing is that if you have a functional group that must be on the end, mainly aldehydes and carboxylic acids, you wouldn't number these because they have to be on the end (obvs) but then when you put other functional groups on you can't start numbering these "end only" functional groups because that would make no sense, it which case you always assume that the "end only" functional group is at 1 and number from there and this overrides the rule about keeping the numbers low.

So for example... 

...is called, 4-Chloro-3-Methyl Butanoic Acid

NOT

1-Chloro-2-Methyl Butan-4-oic Acid

Even though the numbers are kept lower on the alternative name.

The only other thing worth remembering is that of you have more than one of a functional group it becomes, for example, 1,3-dimethyl or 1,3,3-trimethyl and then when you are alphabetising them you go by the "d" or "t" not "m" e.g. it would be "1,3-dimethyl-4-ethyl....." not "4-ethyl-1,3-dimethyl-....."