Two acids corresponding to the formula of Kekule and Claus are triphenyl acrylic acid, (C6H5)2C: C([[Cooh) C 6 H]],, and triphenyl acetic acid, (C,H,),C 000H.
Von Liebig (Ann., 1908, 360, p. 128), from a very complete discussion of triphenyl methane derivatives, concluded that the group i ng A A A was the only true organic chromophore, colour production, however, requiring another condition, usually the closing of a ring.
Busch (Ber., 1905, 38, pp. 856, 4049) has isolated a series of bridged ring compounds which he describes as endo-iminodihydrotriazoles, the triphenyl derivative (annexed formula) being prepared by condensing triphenylaminoguanidine with formic acid.
Heated with anhydrous sodium acetate and acetic anhydride it gives cinnamic acid; with ethyl bromide and sodium it forms triphenyl-carbinol (C 6 H 5) 3 C OH; with dimethylaniline and anhydrous zinc chloride it forms leuco-malachite green C6H5CH[C6H4N(CH3)2]2; and with dimethylaniline and concentrated hydrochloric acid it gives dimethylaminobenzhydrol, C 6 H 5 CH(OH)C 6 H 4 N(CH 3) 2.