Acridine

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 molecule pyridine and quinoline, acridine is mildly basic. It is an almost colorless solid. There are no commercial applications of acridines but at one time acridine dyes were popular. It crystallizes in needles. 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 molecule pyridine and quinoline, acridine is mildly basic. It is an almost colorless solid. There are no commercial applications of acridines but at one time acridine dyes were popular. It crystallizes in needles. Carl Gräbe and Heinrich Caro first isolated acridine in 1870 from coal tar. Acridine is separated from coal tar by extracting with dilute sulfuric acid. Addition of potassium dichromate to this solution precipitates acridine bichromate. The bichromate is decomposed using ammonia. Acridine and its derivatives can be prepared by many synthetic processes. In the Bernthsen acridine synthesis, diphenylamine is condensed with carboxylic acids in the presence of zinc chloride. When formic acid is the carboxylic acid, the reaction yields the parent acridine. With the higher larger carboxylic acids, the derivatives substituted at the meso carbon atom are generated. Other older methods for the organic synthesis of acridines include condensing diphenylamine with chloroform in the presence of aluminium chloride, by passing the vapours of orthoaminodiphenylmethane over heated litharge, by heating salicylaldehyde with aniline and zinc chloride or by distilling acridone (9-position a carbonyl group) over zinc dust. Another classic method for the synthesis of acridones is the Lehmstedt-Tanasescu reaction. In enzymology, an acridone synthase (EC 2.3.1.159) is an enzyme that catalyzes the chemical reaction Thus, the two substrates of this enzyme are malonyl-CoA and N-methylanthraniloyl-CoA, whereas its 3 products are CoA, 1,3-dihydroxy-N-methylacridone, and CO2. 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. It also shares properties with quinoline. Acridines can be reduced to the 9,10-dihydroacridines, sometimes called leuco acridines. Reaction with potassium cyanide gives the 9-cyano-9,10-dehydro derivative. On oxidation with potassium permanganate, it yields acridinic acid (C9H5N(CO2H)2) otherwise known as quinoline-1,2-dicarboxylic acid. Acridine is easily oxidized by peroxymonosulfuric acid to the acridine amine oxide. The carbon 9-position of acridine is activated for addition reactions.