2795. Cytosine

Nomenclature

CAS number: 71-30-7
4-Amino-2(1H)-pyrimidinone; 4-amino-2-oxo-1,2-dihydropyrimidine; 4-amino-2-pyrimidinol; 4-amino-2-hydroxypyrimidine.
C4H5N3O; mol wt 111.10.
C 43.24%, H 4.54%, N 37.82%, O 14.40%.

Description and references

Widely distributed in nature; constituent of nucleic acids. Isoln by hydrolysis of thymus nucleic acids: Levene, Bass, Nucleic Acids (New York, 1931) p 57. Syntheses: Hilbert, Johnson, J. Am. Chem. Soc. 52, 1152 (1930); Hilbert et al., ibid. 57, 552 (1935); cf. Hunter, Hlynka, Biochem. J. 31, 486 (1937); Ballweg, Tetrahedron Lett. 1968, 2171; David, Lubineau, Bull. Soc. Chim. Fr. 1969, 816. Synthesis from carbon dioxide and ammonia on kaolinite: G. R. Harvey et al., Naturwissenschaften 58, 624 (1971). Exists in keto form. Structure: Barker, Marsh, Acta Crystallogr. 17, 1581 (1964); of monohydrate: Jeffrey, Kinoshita, ibid. 16, 20 (1963); R. J. McClure, B. M. Craven, ibid. B29, 1234 (1973). Tautomerism: Y. P. Wong, J. Am. Chem. Soc. 95, 3511 (1973). Review: Ts'o, “Bases, Nucleosides and Nucleotides” in Basic Principles in Nucleic Acid Chemistry vol. 1, P. O. P. Ts'o, Ed. (Academic Press, New York, 1974) pp 453-584.

Chemical structure

Derivative

Monohydrate.

Properties

Lustrous monoclinic or triclinic platelets from water. Anhydr at 100°; brown around 300°; dec 320-325°. uv max (pH 8.8): 196.5, 267 nm (ε × 10-3 22.5, 6.1). pK1 4.60; pK2 12.16. One gram dissolves in 130 ml water. Slightly sol in alcohol, insol in ether. Gives red color when dissolved in soln of sodium hypochlorite to which a drop of NH4OH is added. Forms salts with acids.