Acridine is an organic compound and a nitrogen heterocycle with the formula C13H9N. Acridines are substituted derivatives of the parent ring. It is a planar molecule that is structurally related to anthracene with one of the central CH groups replaced by nitrogen. Like the related molecules pyridine and quinoline, acridine is mildly basic. It is an almost colorless solid, which crystallizes in needles. There are few commercial applications of acridines; at one time acridine dyes were popular, but they are now relegated to niche applications, such as with acridine orange. The name is a reference to the acrid odour and acrid skin-irritating effect of the compound.
Acridine displays the reactions expected of an unsaturated N-heterocycle. It undergoes N-alkylation with alkyl iodides to form alkyl acridinium iodides, which are readily transformed by the action of alkaline potassium ferricyanide to N-alkyl acridones.
Acridine and its homologues are weakly basic. Acridine is a photobase which has a ground state pKa of 5.1, similar to that of pyridine, and an excited state pKa of 10.6.[10] It also shares properties with quinoline.
Several dyes and drugs feature the acridine skeleton.[12] Many acridines, such as proflavine, also have antiseptic properties. Acridine and related derivatives (such as amsacrine) bind to DNA and RNA due to their abilities to intercalate. Acridine orange (3,6-dimethylaminoacridine) is a nucleic acid-selective metachromatic stain useful for cell cycle determination.
At one time acridine dyes were commercially significant, but they are now uncommon because they are not lightfast. Acridine dyes are prepared by condensation of 1,3-diaminobenzene derivatives. Illustrative is the reaction of 2,4-diaminotoluene with acetaldehyde:[13]
Synthesis of C.I. Basic Yellow 9, an acridine dye.
9-Phenylacridine is the parent base of chrysaniline or 3,6-diamino-9-phenylacridine, which is the chief constituent of the dyestuff phosphine (not to be confused with phosphine gas), a byproduct in the manufacture of rosaniline. Chrysaniline forms red-coloured salts, which dye silk and wool in a fine yellow; and the solutions of the salts are characterized by their fine yellowish-green fluorescence. Chrysaniline was synthesized by O. Fischer and G. Koerner by condensing o-nitrobenzaldehyde with aniline, the resulting o-nitro-p-diaminotriphenylmethane being reduced to the corresponding o-amino compound, which on oxidation yields chrysaniline.
Benzoflavin, an isomer of chrysaniline, is also a dyestuff, and has been prepared by K. Oehler from m-phenylenediamine and benzaldehyde. These substances condense to form tetraaminotriphenylmethane, which, on heating with acids, loses ammonia and yields 3,6-diamino-9,10-dihydrophenylacridine, from which benzoflavin is obtained by oxidation. It is a yellow powder, soluble in hot water.[8]
Acridine is known to induce small insertions or deletions in nucleotide sequences, resulting in frameshift mutations.[14] This compound was useful to identify the triplet nature of the genetic codes.[14]
As established by X-ray crystallography, acridine has been obtained in eight polymorphs. All feature very similar planar molecules with nearly identical bond lengths and bond distances.[15][16]
^ abcdAcridine in Linstrom, Peter J.; Mallard, William G. (eds.); NIST Chemistry WebBook, NIST Standard Reference Database Number 69, National Institute of Standards and Technology, Gaithersburg (MD) (retrieved 2014年06月22日)
^Maier W, Baumert A, Schumann B, Furukawa H, Gröger D (1993). "Synthesis of 1,3-dihydroxy-N-methylacridone and its conversion to rutacridone by cell-free extracts of Ruta-graveolens cell cultures". Phytochemistry. 32 (3): 691–698. Bibcode:1993PChem..32..691M. doi:10.1016/S0031-9422(00)95155-0.
Schmidt A, Liu M (2015). Recent Advances in the Chemistry of Acridines. Advances in Heterocyclic Chemistry. Vol. 15. pp. 287–353. doi:10.1016/bs.aihch.201504004. ISBN9780128021293. [review article dealing with physical properties of acridines, natural products possessing the acridine core, biologically active acridines, applications of acridines, new syntheses and reactions of acridines]
