Cytosine

Cytosine (/ˈsaɪtəˌsiːn, -ˌziːn, -ˌsɪn/) (symbol C or Cyt) is one of the four nucleobases found in DNA and RNA, along with adenine, guanine, and thymine (uracil in RNA). It is a pyrimidine derivative, with a heterocyclic aromatic ring and two substituents attached (an amine group at position 4 and a keto group at position 2). The nucleoside of cytosine is cytidine. In Watson–Crick base pairing, it forms three hydrogen bonds with guanine.

Not to be confused with cytokine, cytidine, cysteine, cystine, or cytisine.
Cytosine
Names
Preferred IUPAC name
4-Aminopyrimidin-2(1H)-one
Other names
4-Amino-1H-pyrimidine-2-one
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.000.681
KEGG
MeSH Cytosine
PubChem CID
UNII
  • InChI=1S/C4H5N3O/c5-3-1-2-6-4(8)7-3/h1-2H,(H3,5,6,7,8) Y
    Key: OPTASPLRGRRNAP-UHFFFAOYSA-N Y
  • InChI=1/C4H5N3O/c5-3-1-2-6-4(8)7-3/h1-2H,(H3,5,6,7,8)
    Key: OPTASPLRGRRNAP-UHFFFAOYAY
SMILES
  • O=C1Nccc(N)n1
Properties
C4H5N3O
Molar mass 111.10 g/mol
Density 1.55 g/cm3 (calculated)
Melting point 320 to 325 °C (608 to 617 °F; 593 to 598 K) (decomposes)
Acidity (pKa) 4.45 (secondary), 12.2 (primary)
Magnetic susceptibility (χ)
 -55.8·10−6 cm3/mol
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Y verify (what is YN ?)
Infobox references
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