- Adenine: 9H-purin-6-amine (IUPAC Name), 6-aminopurine (Other Name)
- Guanine: 2-amino-1H-purin-6(9H)-one (IUPAC Name), 2-amino-6-hydroxypurine (Other Name)
- Xanthine: 3,7-Dihydropurine-2,6-dione (IUPAC Name), 1H-Purine-2,6-diol (Other Name)
- Hypoxanthine: 1H-purin-6(9H)-one (IUPAC Name), 6-oxypurine (Other Name)
The examples of pyrimidines of common occurrence are listed below.
- Thymine: 5-Methylpyrimidine-2,4(1H,3H)-dione (IUPAC Name), 5-methyluracil (Other Name)
- Uracil: Pyrimidine-2,4(1H,3H)-dione (IUPAC Name), 2,4-dihydroxypyrimidine (Other Name)
- Cytosine: 4-aminopyrimidin-2(1H)-one (IUPAC Name), 4-amino-1H-pyrimidine-2-one (Other Name)
Chemical properties of pyrimidines are similar to that of pyridines. Pyrimidines are the compounds produced through the process of organic synthesis. One of the methods through which pyrimidines can be synthesized artificially is the Biginelli reaction.
Pyrimidines are aromatic heterocyclic organic compounds that consist of a pyrimidine ring which is fused to a ring of imidazole. Molecules like guanine and adenine are derivatives of a class called purine – which is not a real molecule in itself. In short, these derivatives are manifestation of a ‘virtual’ class called purine. Adenine and guanine are the purines which participate in DNA synthesis through high-energy bonding. Purines and pyrimidines participate in the growth of RNA and DNA through a process called transcription or DNA replication. Short-term energy storage is also one of the functions of these nucleotides.
In the process of nucleotide synthesis, purines and pyrimidines form hydrogen bonds with each other. The structure of nucleotides is such that three hydrogen bonds are formed between guanine and cytosine while adenine and thymine form two hydrogen bonds with each other. Such type of bonding is referred as base pairing.
- Purines have higher melting and boiling points than pyrimidines. The reason behind this difference in melting and boiling points is that the molecules of purines are complex and heavy. Purines participate in greater number of molecular reactions in comparison to pyrimidines.
- Purines are known to act as precursor molecules in the synthesis of chemical compounds like theophylline, theobromine, caffeine, etc. Pyrimidines are not known to function as precursor molecules.