TRIPHENYLMETHANE (

See also:

• C6H6

C6H6)3CH  , a hydrocarbon, important as being the parent substance of several series of exceedingly valuable dyestuffs, e.g. rosanilines and malachite greens derived from aminotriphenylmethanes, and aurins and phthaleins de-rived from oxytriphenylmethanes . It is obtained by condensing benzal chloride with mercury diphenyl (Kekule and Franchimont, Ber., 1872, 5, p . 9c7-); from benzal chloride or benzotrichloride and zinc dust or aluminium chloride; from chloroform or carbon tetrachloride and benzene in the presence of aluminium chloride; and deamidating di- and tri-aminotriphenylmethane with nitrous acid and alcohol (0. and E . Fischer, Ann., 1881, 206, p . 152) . The last reaction is most important, for it established the connexion between this hydrocarbon and the rosanilines . Triphenylmethane is a white crystalline solid, melting at 92° and boiling at 358° . It separates from benzene and thiophene with one molecule of the " solvent of crystallization." On oxidation it gives triphenylcarbinol, (C6H5)3C•OH, and reduction with hydriodic acid and red phosphorus gives benzene and toluene . It combines with potassium to give (C6H5)3CK, which with carbon dioxide gives potassium triphenylacetate, (C6H5)3C CO2K . Fuming nitric acid gives a paratrinitro substitution derivative which on reduction gives paraleucaniline; the salt of the carbinol formed on oxidizing this substance is the valuable dye rosaniline . Considerable interest is attached to the remarkable series of hydrocarbons obtained by Gomberg (Ber., 1900, 33, p . 3150, et seq.) by acting on triphenylmethane chloride (from triphenylmethane carbinol and phosphorus pentachloride, or from carbon tetra-chloride and benzene in the presence of aluminium chloride) and its homologues with zinc, silver or mercury .

Triphenylmethane chloride yields triphenylmethyl; ditolylphenylmethyl and tritolylmethyl have also been prepared . They behave as unsaturated compounds, combining with

oxygen to form peroxides and with the halogens to form triarylmethane halides . Triphenylmethyl also combines with ethers and esters, but the compounds so formed are unsaturated . In the solid state triphenyl is colourless, crystal-line and bimolecular . It was thought that it might be identical with hexaphenylethane, but the supposed synthesis of this sub-stance by Ullmann and Borsum (Ber., 1902, 35, p . 2897) appeared to disprove this, although it showed that triphenylmethyl readily isomerized into their product, under the influence of catalysts . A.E . Tschitschibabin (Ber., 1908, 41, p . 2421), however, has shown that Ullmann and Borsum's preparation was para-benzhydroltetraphenylmethane (C6H5)2CH•C6H4•C(C6H5)3; and the view that solid triphenylmethyl is hexaphenylethane has much in its favour . Another remarkable fact is that these substances yield coloured solutions in organic solvents; triphenylmethyl gives a yellow solution, whilst ditolylphenyl and tritolylmethyls give orange solutions which on warming turn to a violet and to a magenta, the changes being reversed on cooling . Several views have been published to explain this fact . A summary is given by Tschitschibabin (Journ. prak .

Chem., 1907 (ii.), 74, p . 340) . It appears probable that the solutions contain a quinonoid modification (ssee Gomberg and

Cone, Ann., 1909, 370, p . 142) .