Acid-base equilibrium constant and dipole moment of tribenzylammonium picrate in benzene from measurements of dielectric constant

Abstract

The equilibrium con stant for the dissociation of triben zy lammonium picrate in t o picric acid and t riben zylamine in ben zene at 30° a nd 40° C has been d eterm ined from the variation of dielectric consta n t wi th con cen tration. The heat of r ea ction is in t he neighborhood of 11.4 kilocalories per mole. The dipole m om en t of t ribenzyla mmonium picrate, ] 2.0 X 1O-18esu , is substantially t he saIne a s found previously for t he picra tes of t he m ore s tron gly basic alk ylamines. The dipole mom ent of picri c acid, 1. 75 X 1O-18esU , was a lso determin ed .

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

“…It is of particular interest that the association constant for the reaction of tribenzylamine with picric acid in benzene is the same as the value obtained from measurements by Maryott of the dielectric constant of benzene solutions of tribenzylammonium picrate [25]. The suggestion has been made [26 , 27] that tribenzylammonium picrate may exis t in isomeric forms, RaN.HPi and R aNH+Pi-, which are slowly interconvertible, but the arguments used in support of this hypothesis are not entirely convincing.…”

“…The suggestion has been made [26 , 27] that tribenzylammonium picrate may exis t in isomeric forms, RaN.HPi and R aNH+Pi-, which are slowly interconvertible, but the arguments used in support of this hypothesis are not entirely convincing. N o anomalies that might b e explained on this basis were observed in spectrophotometric studies of the r eaction of tribenzylamine wi th picric acid in benzene [20], and Maryott, in measuring the dipole moment of tribenzylammonium picrate, could not detect such an equilibrium [25] . Wi tschonke and Kraus [28] were also unable to furnish exp erimental support for such an isomerism.…”

Brønsted Acid—Base Behavior in “Inert” Organic Solvents

“…A - (14) In a majority of the cases studied there is evidence (see Section VI) that the addition product consists of hydrogen-bonded ion pairs. .…”

“…In further support of the hypothesis of cation-anion bonding in ammonium and hydroxyammonium salts, Witschonke and Kraus 165 found that their ion-pair dissociation in nitrobenzene is promoted by adding various bases (water, pyridine, triethylamine, and piperidine). Subsequently, Maryott 14 dipole moments of additional salts, including primary and secondary ammonium picrates. Kraus 177 and co-workers found that quaternary and tertiary ammonium picrates and halides have large polar (dipole) moments in benzene solution.…”