Solid-liquid Equilibria for the Quinoline-indole, Isoquinoline-indole, 2-Methylquinoline-indole and 2-Methylquinoline-isoquinoline Systems

Solid-liquid equilibria of the four binary systems of quinoline-indole, isoquinoline-indole, 2-methyl-quinoline-indole, and 2-methylquinoline-isoquinoline were determined, using a visual observation method and differential scanning calorimetry in temperature range from 250 to 330 K. Eutectic phase diagrams were confirmed for these four systems. In the three systems containing indole, it was found that addition compounds formed. For isoquinoline-indole and 2-meth-ylquinoline-indole systems, stoichiometry rations of the first component to indole of the addition compounds were 1:1. From infrared spectroscopy analysis, a N-H-N type hydrogen bonding between isoquinoline and indole was confirmed. For quinoline-indole system, two types of addition compound were observed, of which stoichiometry rations of quinoline to indole were 1:1 and 2:1. From dissociation equilibrium relations and material balances, the equations for mole fractions of pure and addition compounds were derived, using dissociation constants as variables. Based on these equations, solid-liquid equilibria for the systems which form addition compounds were correlated.