Triphenylmethane dyestuffs

Its chief importance is as a source of cinnamic acid by condensation with sodium ethan-oate and ethanoic anhydride and as a source of triphenylmethane dyestuffs by condensation with pyrogallol, dimethylaniline, etc. It is also used in the manufacture of perfumes. 

Presumably the active chlorine of the chloramines formed by reaction with chlorine gas or hypochlorite reacts with TDM in the presence of acetic acid to yield dark blue, mesomerically stabilized quinoid reaction products that possibly rearrange to yield triphenylmethane dyestuffs. 

Phenols are probably initially oxidized to quinones, which then presumably react further to yield triphenylmethane dyestuffs. 

The needle-like shape of the crystals prevents their being easily poured (into the capsule) making them liable to felt so the aim is to produce short crystals either by a suitable selection of conditions for the reactions of diazotization and precipitation of the product (D. Smolenski and Plucinski [13]) or by the addition of certain substances to the solution from which the product is to be precipitated Garfield [14], for instance, suggests for this purpose the addition of triphenylmethane dyestuffs to the solution. 

On crystallization nitromannitol forms needles which easily felt together into an unpourable mass which makes filling the detonators practically impossible. The crystallization process is therefore carried out so as to precipitate the product as granules, by adding protective colloids, triphenylmethane dyestuffs or similar substances. 

Adding to ammonium nitrate small quantities of Acid Magenta, a tri-sulpho-triamine-methyl-triphenylmethane dyestuff. According to Butchart and Whetstone [7] 0.1% of this dyestuff admixed with a saturated ammonium nitrate solution or 0.03% of the dye added to the crystals forms an effective layer that prevents ammonium nitrate from caking within the temperature range —18 to 32°C. 

Fuchsitt test Dilute solutions of triphenylmethane dyestuffs, such as fuchsin (for formula, see Section IV. 15, reaction 9) and malachite green, are immediately decolourized by neutral sulphites. Sulphur dioxide also decolourizes fuchsin solution, but the reaction is not quite complete nevertheless it is a very useful test for sulphur and acid sulphites carbon dioxide does not interfere, but nitrogen dioxide does. If the test solution is acid, it should preferably be just neutralized with sodium hydrogen carbonate. Thiosulphates do not interfere but sulphides, polysulphides, and free alkali do. Zinc, lead, and cadmium salts reduce the sensitivity of the test, hence the interference of sulphides cannot be obviated by the addition of these salts. 

Basic triphenylmethane dyestuffs mostly form sulphonic acids these are generally acid dyestuffs, and when observed in the free state or in form of their acid salts have the same colour as the... 

Quinoline red may be regarded as analogous in constitution to the triphenylmethane dyestuffs, the methane carbon atom of the benzotrichloride entering into two quinoline residues. 

The triphenylmethane dyestuffs, whose somewhat complicated chemistry is... 

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). 

The basic triphenylmethane dyestuff fuchsin (C.I. Basic Violet 14), is decolorized by bisulfite (see page 447). The colorless solution is turned blue by free bromine due to the formation of a brominated dyestuff. Neither free chlorine nor iodine tint fuchsin-bisulfite solution, and so the reaction is suitable for the detection of even small amounts of bromide in chlorides and/or iodides. 

Thiosulfates, polythionates and hydrosulfides are without effect on solutions of triphenylmethane dyestuffs mono- and polysulfides react in the same way as sulfites. 

There are two main types of indicator. One involves a complex of a metal ion, which changes colour when the oxidation state of the metal ion changes. The iron-1,10-phenanthroline system is a typical example, the iron(//) chelate (ferroin) being red, the iron(//7) chelate (ferrion) being essentially colourless (actually very pale blue). The transition potential is about 1,1 V, so the indicator is very suitable for use in titrations with cerium(Ty) in sulphuric acid. The second type of indicator comprises various types of organic compound (aromatic amines, triphenylmethane dyestuffs, for example) which can be oxidised and reduced reversibly, and change colour on doing so. 7V,iV -Diphenylbenzidine is a typical example. 

The triphenylmethane dyestuffs, whose somewhat complicated chemistry is discussed in Section 10.2, show a very remarkable increase in basic strength on AT-alkylation. It can be seen from Table 2.6 that antibacterial activity is strongly correlated with ionization for the substances examined, and that the antibacterial activity thus depends on the presence of chemically inert groups . 

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