Conductometric Analysis of inary Amine Mixtures eacting via pparent Fractional Order Kinetics Ronald A. Greinke and Harry B. Mark, Jr. Department of Chemistry, Unicersity o,f Michigan, Ann Arbor, Mich.
A pseudo fractional-order differential reaction rate method has been developed for the kinetic analysis of binary amine mixtures reacting with the reagent, methyl iodide. The apparent fractional order can possibly result from either hydrogen bonding solvents, side reactions, or change in the amine environment as the reaction proceeds. Errors in the conductometric analysis of amine mixtures which resulted from ion pair formation and from a difference in mobility of the two product ions formed were eliminated by employing smaller initial concentrations of amines and by calibrating the molar changes in conductance for each reacting amine. Of several polar solvents tested, acetonitrile was the most suitable reaction medium. RECENTLY, the differential reaction rate method of Roberts and Regan ( I ) was applied to the analysis of binary mixtures of amines employing their competitive reaction with the common reagent ( Z ) , methyl iodide ([amines] >> [methyl iodide]) forming the ammonium salt. Because primary, secondary, and tertiary amines react with methyl iodide their reaction was found to be more general than others previously used to determine mixtures of amines (2). Prior determination of the rate constants of the two amines in the mixture is necessary when employing the method of Roberts and Regan (3). Hence, as pointed out previously (2), any unknown catalyst or impurity present in the amine mixture may alter the rate constants significantly and produce large errors. If an unknown impurity is present, one can resort to the graphical extrapolation method where prior knowledge of the rate constants is not essential (2,3). Because the rates of reaction of amines with methyl iodide are greatly influenced by the presence of many likely impurities, the analysis of amine mixtures by the graphical extrapolation method (4) ([amines]
