Ultrasonic Studies of Intermolecular Interactions in System Methanol-N,N-Diisobutylformamide

The ultrasonic velocity and density of methanol solutions of N,N-diisobutylformamide (DBFA) were measured at -5, 5 and 15° C over the entire concentration range. The compressibility, excess compressibility, partial molar compressibility, excess molar volume, partial molar volume were calculated. The concentration dependencies of the velocity and density are nonlinear. On taking account of the results for excess molar volume and excess molar compressibility, the minima of these functions are ascribed to the complex formation type CH$\text{}_{3}$OH:DBFA and CH$\text{}_{3}$OH:2 x DBFA. These complexes are formed by hydrogen bond between methanol and N,N-diisobutylformamide molecules. The strong changes in the concentration dependencies of partial molar volume and partial molar compressibility (within range 0...0.1 mol. fraction amide) show that methanol and DBFA have strong interactions in the low-mole-fraction regions, too.