Triphenylmethane, bromine reaction

Troth (32) has studied the polymerization of vinyl acetate in the presence of triphenylmethane and observed the effects discussed above. In practice, there are complications resulting from reactions involving the initiator radicals and the transfer agent. These complications were found also when carbon tetrabromide was used as a transfer agent in the polymerization of styrene in this case, the bromine contents of the polymers were determined by neutron activation analysis (17). 

Phenol Red (the triphenylmethane dye phenolsulphonaphthalein, formula 12.1) reacts with bromine to form tetrabromophenolsulphophthalein (Bromophenol Blue). The change in colour of a solution at pH 5.5 from yellow to violet is very pronounced. The reaction has been the basis of a sensitive spectrophotometric method of determining bromine [1,6-9]. The molar absorptivity, e, of the violet produet at X ,ax = 580 nm is 1.14-10 (a = 0.14). 

Chemiluminescence is observed during the reactions of aryl Grignard reagents with oxygen 4650 or with aryl peroxides.4656 Analysis of the luminescence spectrum and e.s.r. data indicates that for the oxygen-induced reaction brominated biphenyls are the emitters, whereas in the peroxide case triphenylmethane is the luminescent species. 

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. 

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