DIBENZANTHRONE

Description

Violanthrone, Indanthren Dark Blue BOA,is generated by potash fusion of benzanthrone , . Direct potash fusion leads to side products, such as isoviolanthrone and 4-hydroxybenzanthrone. The crude product may be used directly or in mixtures with other dyes in vat dyeing. It is also used to generate violanthrone derivatives. Several processes have been developed to decrease the amounts of undesirable side products of the direct potash fusion of benzanthrone or to purify the bibenzanthronyl or the crude violanthrone . Especially effective is the addition of high-boiling solvents such as naphthalene, the so-called low carbazole anthracene residues, or sodium acetate to the melt. The quality of the products prepared by these methods is satisfactory for the production of almost all violanthrone dyes.

General Description

Bluish-black to black powder.

Air & Water Reactions

Insoluble in water.

Fire Hazard

Flash point data for DIBENZANTHRONE are not available. DIBENZANTHRONE is probably combustible.

Flammability and Explosibility

Not classified

Synthesis

Violanthrone of high purity is obtained from 4,4'-bibenzanthronyl (153) by alkaline or acid ring closure, preferably in the presence of oxidizing agents , . If this ring closure is carried out in sulfuric acid with an excess of manganese dioxide, the 16,17- violanthronequinone (155) is obtained. This can be reduced readily with sodium hydrogen sulfite to 16,17-dihydroxyviolanthrone (156). Subsequent alkylation of the hydroxy groups yields very fast navy-blue to brilliant-green vat dyes. The dimethyl ether (157) is the well-known dye Caledon Jade Green or Indanthren Brilliant Green B and FFB (extremely pure form).

Properties and Applications