Wikipedia:  

Cytosine

2(1H)-Pyrimidinone, 4-amino-; 4-Amino-2(1H)-pyrimidinone; Cytosinimine; CYTOSINE; Cytosine; 4-Amino-2-hydroxypyrimidine; Cyt
Molecular Formula
C4 H5 N3 O
Natural Isotopic Abundance Mass
111.102
Mono-Isotopic Molecular Masses
C12N14:   111.0432617982
C13N14:   115.0566811494
C12N15:   114.0343664778
C13N15:   118.0477858290
Cytosine image
Cytosine
InCHi String:
InChI=1S/C4H5N3O/c5-3-1-2-6-4(8)7-3/h1-2H,(H3,5,6,7,8)

canonical and isotoopic SMILES:
C1=C(NC(=O)N=C1)N


PUBCHEM iupac NAME: PUBCHEM iupac TRADITIONAL NAME: PUBCHEM iupac OPENEYE NAME: PUBCHEM iupac CAS NAME: PUBCHEM iupac SYSTEMATIC NAME
cytosine



PubChem Substance (SID):   85165003   149206   3670
PubChem Compound (CID):   597
KEGG: Compound ID   C00380
CAS Registry IDs:   118511-36-7   14987-28-1   26661-23-4   504-05-2   66322-75-6   71-30-7
PDB Chemical Component   CYT
Miscellaneous Databases and IDs:   CHEBI 16040   EINECS 200-749-5   NSC 27787

Reference data were obtained primarily from the PubChem database.

Three dimensional molecular rendering uses Jmol.