Acid-base reactions in benzene and other organic solvents: Behavior of bromphthalein magenta with different classes of organic bases

Abstract

Practical and theoretica l aspects of acid-base reactions in benzene and other organic solvents al'e discussed . The synthesis of the indicators bromphtha lein magenta E and B (the ethyl and n-butyl esters of t etrabromopheno lph thale in ) an d of their t etraalkylammonium salts is descri bed. Qualitative and spectrophotometric data concern in g the color reactions of the indicators with primary, seconda ry, and t ertia ry a li phatic amines , s ubstituted guan idines, a nd other n itrogen bases in benz ene and other types of organic solvents are presen ted. An expla nati on off ered for the color phenom ena is also appli cable to ulfon ephthalcins and other indicators.Examples are given of the qu antitative m eas urement of the relative reactivity of bases with bromphthal ein magenta in benzene. Illust rations a re furnishe d of the app li cation of the ind icato rs to the quantitative estimation of acids and bases, to measu rem ents of the relative s trengt,h s of orga ni c acids, and to the differen tiation o f primary, secondary, and tertiary a liphatic a mines.During t he sp ectrophotometric inves t igations, it was necessar y to des ign new types of a bsorption cells s uitable fo r vo latile solvents a nd for th in laye rs of solu t ion. A desc ription of the e cells is given.

X-ray crystal structure determination and NMR solution studies of 3′,3″5′,5″-tetrabromophenolphthalein ethyl ester

“…The title compound was synthesized by procedures presented previously (2,5). Pertinent data about the crystal used and the measurement of diffraction intensities are summarized in Table 1.…”

Behavior of bromophthalein magenta E (tetrabromophenolphthalein ethyl ester) with organic bases and its bearing on the Bronsted-Lowry and Lewis concepts of acidity

“…Provisional values of the association con tant were given previously for triethylamine, diphenylguanidine, and di-o-tolylguanidine [1]. It wa desirable to check some of these measurements with better control of the temperature than was feasible formerly and at additional concentraLions made po sible by the acquisition of shorter absorption cells.…”

“…A solution of a quaternary ammonium salt of bromophthalein magenta E in an inert solvent is blue, without a purple tinge. An explanation of this differentiating behavior of bromophthalein magenta E toward different classes of bases was presented in the reference cited [1].…”

“…However, various dyes that are described in the literature or known to dye manufacturers would probably prove very useful if made available to investigators. For example, the compound termed by us "bromophthalein magenta E" has been known since 1897 [14], although its potential use as an indicator of basicit in inert solvents was not known until a systematic search at this Bureau for suitable indicators disclosed its valuable properties [1].…”

“…Indicator dyes, if available, would b e particularly useful for solu tions of acids and bases in inert solvents like benzene, because such solutions do no t contain significan t quan tities of free hydrogen ions, and measurements by m eans of the hydrogen or glass electrodes are therefore not applicable. In a previous paper [1],2 th e preparation of the acidic indicator dye, bromophthalein magenta E (th e ethyl ester of tetrabromophenolphthalein), was described and a compreh ensive s urvey of its reactions with organic bases in benz en e and som e other organic solvents was presented. A quartz photoelectric spectrophotometer was used in following the course of th e reactions.…”