New nitrogen substd. phenol red dyes and sulphonaphthalein - having amino or nitro gps. and prepn. from amino sulphobenzoic anhydride and phenols and bondable to e.g. polymeric matrix for pH indicators

摘要

A nitrogen-substd. sulphonephthalein (1) has a sulphonated phenyl gp. bonded to a carbon atom and a nitrogen-contg. gp. The nitrogen atom is in the para position to the bonded carbon atom. Also claimed are an amino-substd. phenol-red cpd. and its prepn.; nitrogen-contg. phenol-red cpds. of specified structures and their prepn.; the use of these cpds. in dye-polymer compositions, fibre-optic probes and pH measuring compositions and a polymeric indicator or polymer mixture where an amino gp. substd. sulphonephthalein is covalently bonded to the polymer, and their prepn.. Pref. (1) contains amino or nitro gps. as nitrogen - contg. gps. and (1) is selected from the group of phenol-sulphnoephthaleins, cresol-sulphonephthaleins and thymol-sulphone phthaleins. Specifically claimed is 4-amino-phenol-sulphonephthalein. The N-contg. phenol-red cpd. is of formula (2) where X = amino or nitro, and X is in the 3,4,5 or 6 position, pref. in the 4 position (separately claimed). ADVANTAGE - The cpds. can be immobilised on a carrier with minimal effect on their dyestuff functionality, e.g. minimal displacement of the pKa value. The polymer mixtures give clear, homogeneous, mechanically stable films which are water-insoluble with low permeability.