Question

What functional groups are there in caffeine?

Answer 1

Its IUPAC name is 1,3,7-trimethyl-1H-purine-2,6(3H,7H)-dione 3,7-dihydro-1,3,7-trimethyl-1H-purine-2,6-dione.
When you read this IUPAC name you can see that it is a ketone so it has carbonyl group.

In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom: C=O. It is common to several classes of organic compounds, as part of many larger functional groups.

Also, you can see amine group but they don't have priority,

Answer 2

The functional groups in caffeine are amine and amide.

Explanation:

The structure of caffeine is

Let's look first at the 5-membered ring.

The two N atoms are part of amine groups.

The `"C=C"` and `"C=N"` bonds look like functional groups, but they are neither alkene nor imine groups.

They are both part of the 5-membered system called an imidazole ring.

An imidazole ring is aromatic, like benzene.

Now let's look at the 6-membered ring.

The C=O and N groups look like ketone and amine groups, but they are not.

A C=O next to an N is an amide group.

There are two amide groups in the ring.

So caffeine contains two amine and two amide functional groups.