# How can you determine if a compound is a purine or pyrimidine?

Jan 20, 2017

A pyrimidine has one ring; a purine has two rings.

The pyrimidines ($\boldsymbol{\text{C}}$ytosine, $\boldsymbol{\text{U}}$racil, and $\boldsymbol{\text{T}}$hymine) all have one ring.

The purines have two rings.

One way to remember the difference is:

The pyrimidines are C U T from the purines.

If they were no labels in the picture below, could you identify the purines and the pyrimidines?