Disazo Dyes of the Type -2
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Almost all members of this type of dyes belowng to direct dyes class. L, the linking bridge can be built up by making use of a condensing agent like phosgene (COCl2) and cyanuric chloride (463). Schemes are already discussed in the syntheses of green dyes (82) and (496) from a yellow dye Dy-NH2 (80) and a blue dye DB—NH2 (81) involving phosgenation and cyanuration respectively. Another way is to have the linking bridge, L such as —NH—, —NHCONH— and other complex bridging groups in the component Z—L—Z as in the cases of Di-J-acid (556) and J—acid—urea (385).
One example of this type of disazo dye is chlorazol scarlet 4 BS, where, A is aniline, Z—L—Z is J—acid—urea, (385) and A1 is p-amino acetanilide (289).In general, many direct dyes, acid dyes, food colours, mordant dyes, solvent dyes, disperse dyes, cationic dyes and reactive dyes belong to disazo dyes depending upon the specific structural requirments. However, for the sake of simplicity these classes by applications are not discussed individually.
