Sulphonamides general structure

Theoretical explanations for the effects of substituents on the hue of diphenylpyrazoline brighteners have been published by Glisten and co-workers [46,47]. In practice almost all commercially important diphenylpyrazoline FBAs have the general structure 11.30, in which S02R is a sulphone or sulphonamide grouping. 

The fundamental basis of the prevailing structural resemblance of sulphanilamide-in particular and sulphonamides-in general to /j r -aminobenzoic acid (PABA) which is so destructive to these microorganisms is foimd to be quite evident. 

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