Acid-base reactions in organic solvents; behavior of some halogenated derivatives of phenolsulfonephthalein with different classes of organic bases in benzene.

This paper, the second in a series concerning the use of indicator dyes to study the reactions of organic acids and bases in organic solvents, deals with halogen derivatives of phenolsulfonephthalein. Spectrophotometric data are given for mixtures of bromocresol green, bromophenol blue, iodophenol blue, and tetrabromophenol blue with primary, secondary, and tertiary aliphatic amines in benzene; and qualitative data are tabulated for chlorophenol blue, bromochlorophenol blue, chlorophenol red, bromophenol red, bromocresol purple, and bromothymol blue. Comparisons are made of the phenolsulfonephthaleins and the bromophthalein magentas. The structural changes that accompany the color phenomena are discussed. Suggestions are made regarding the use of the indicators in inert solvents.