Adenine is a purine base, one of the four nucleobases in the genetic code of DNA and RNA. Its chemical formula is C5H5N5. The molecular structure of adenine can be described as a flat, six-membered ring (a purine ring) with two nitrogen-containing groups, an exocyclic amino group on position 6 and an amino group on position 1.

Adenine is an aromatic compound, meaning that it has a ring of conjugated double bonds that makes it stable and resistant to chemical reactions. The nitrogen atoms within the purine ring participate in hydrogen bonding, allowing adenine to form base pairs with other nucleobases. Specifically, adenine forms base pairs with thymine in DNA and with uracil in RNA through hydrogen bonds between the amino group of adenine and the keto group of thymine or uracil. These base pairings are essential for the genetic information encoded in DNA and RNA to be accurately copied, transcribed, and translated during various cellular processes.