Patents triphenylmethane dyes

Azo dyes Allura Red AC, Amaranth, Azorubine, Brilliant Black BN, Brown FK, Brown HT, Lithol Rubine BK, Ponceau 4R, Red 2G, Sunset Yellow, Tartrazine Triarylmethane (triphenylmethane) dyes Brilliant Blue FCF, Fast green FCF, Green S, Patent Blue V... 

Based on synthetic work that Cescon, Jenkins, Balon and I did, Looney calculated some structural changes for triphenylmethane dyes, which resulted in two patents. 

The chlorine atom in o-chlorobenzaldehyde is easily replaceable by a sulfo group by heating the chloro compound with neutral sulfite at 150°C. Ortho sulfo-nated benzaldehyde give alkali fast triphenylmethane dyes (patent blue, erioglau-cine, xylene blue). 

Xylene blue belongs to the group of so-called patent blues which are sulfonated triphenylmethane dyes that are stable to alkali. The dyes are all characterized by having a sulfo group in the position ortho to the central carbon atom as in the following general formula ... 

One example of the role of basic research in the 1930s is the work of Bemd Eistert, one of the earliest proponents of mesomerism in Germany, for which purpose he collaborated with his former teacher Fritz Arndt. Eistert joined BASF in 1929, and he took appointments in Oppau, at the Central Research Laboratory, at the triphenylmethane dyes department, and the patent department. It seems, however, as if his theoretical studies were done in a rather private way, and were not related to his tasks in the industrial departments. In the years after 1932, and especially with the appointment of Walter Reppe in 1938, the investigations at the Central Laboratory were directed towards pioneering technological research, not towards a deeper understanding of corporate-related science and technology. 

With the invention of acid magenta (1877) and fast red AV (1878), Caro successfully established BASF in both the field of acidic triphenylmethane dyes and the newly revived field of azo dyestuffs. The most important criterion for his success was a careful study of trends in the dyestuff industry. In particular it was essential to enter into manufacture of novel dyes not long after they had been introduced by competitors. To achieve this it was necessary to analyse new dyestuffs, improve on the manufacturing processes and, in the best case, invent patentable analogues or improvements. Here I consider one example, in order to make clear the method of invention in Caro s laboratory. 

A useful classification of sensitizing dyes is the one adopted to describe patents in image technology. In Table 1, the Image Technology Patent Information System (ITPAIS), dye classes and representative patent citations from the ITPAIS file are Hsted as a function of significant dye class. From these citations it is clear that preferred sensitizers for silver haUdes are polymethine dyes (cyanine, merocyanine, etc), whereas other semiconductors have more evenly distributed citations. Zinc oxide, for example, is frequendy sensitized by xanthene dyes (qv) or triarylmethane dyes (see Triphenylmethane and related dyes) as well as cyanines and merocyanines (see Cyanine dyes). 

Towards the end of the 19th century, many of the newly established firms developed aniline- and triphenylmethane dyestuffs. In 1859, Ciba began the production of fuchsine, which enabled the dyeing of silk. In 1877, BASF was granted the first German patent for a coal tar dye entitled Preparation of Blue Dyestuffs from Dimethylaniline (viz. Methylene Blue) (Fig. 2.2). 

Synonyms Acid blue 3, calcium salt (2 1) Cl 42051 N-[4-[[4-(Diethylamino) phenyl] (5-hydroxy-2,4-disulfophenyl) methylene]-2,5-cyclohexadien-1 -ylidene]-N-ethylethanaminium, hydroxide, inner salt, calcium salt (2 1) Ethanaminium, N-[4-[[4-(diethylamino) phenyl] (5-hydroxy-2,4-disulfophenyl) methylene]-2,5-cyclohexadien-1-ylidene]-N-ethyl-, hydroxide, inner salt, calcium salt (2 1) Food blue 5 m-HydroxytetraethyIdiaminotriphenylcarbinol anhydride disulfonic acid calcium salt Patent blue Patent blue V Patent blue violet Ciassification Triphenylmethane color Empiricai Cs4H62CaN40i4S4 Properties M.w. 1159.52 Toxicoiogy LD50 (IV, rat) 5 g/kg, (IV, mouse) 1200 mg/kg mod. toxic by IV route TSCA listed Hazardous Decomp. Prods. Heated to decomp., emits toxic vapors of NOx and SOx Uses Dye for wool colorant in foods, hair dyes Manuf./Disthb. AB R Lundberg Dudley... 

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