Pyrimidines

Pyrimidine is a six-membered heterocyclic compound that includes nitrogenu heteroatoms in the 1 and 3 positions. The system of conjugated bonds determines its aromatic character.

Chemical properties
Pyrimidine has ``basic properties'' due to the free electron pairs of both nitrogens. At the same time, however, the energy of the π-electrons decreases and the molecule is less prone to electrophilic substitution and, conversely, more prone to nucleophilic substitution.

Pyrimidine derivatives
Pyrimidine is the basis of some nitrogenous bases: thymine, uracil and cytosine. These are attached via an N-glycosidic bond to ribose or deoxyribose and form nucleosides. Thymine is found in DNA, while uracil is found in nature only in RNA. Both are complementary to adenine, to which they are linked by two hydrogen bonds. Cytosine is complementary to guanine and forms three hydrogen bonds.

In addition to the main bases, minor bases can also occur (e.g. 5-methylcytosine', 5-hydroxymethylcytosine',...)

Pyrimidine is also part of vitamin B1.

Related Articles

 * Disorders of pyrimidine metabolism
 * Nucleotide Metabolism