SOLUTION CHEMISTRY OF ETHYLMETHYLGLYOXIME .I. PROTON COMPLEX

The solubility of ethylmethylglyoxime (EMG) was studied as a function of pH. The solubility Ksl in 0.1 M aqueous solution is 0.0132 ±0.0006 M. The distribution constants KDl of EMG between various organic solvents and 0.1 M aqueous solution were found to be -0.47 for chloroform, -0.51 for benzene, -1.10 for carbon tetrachloride and -1.83 for hexane. The acid dissociation constants were determined from potentiometric titrations; the values pKa1=10.51 and pKa2=12.02 were obtaining by fitting the experimental data to normalized curves. The UV spectra of 5·10-5 M EMG solutions of varying pH were measured between 210 and 290 nm. It is shown that H2A has an absorption maximum at 226 nm and HA-and A2- have absorption maxima at nearly the same wavelengths, i.e. 258 and 266 nm, respectively. The spectra of HA- and A2- have approximately the same form. The data are compared with those of dimethylglyoxime (DMG). The distribution constants (org/aq) are 4-5 times higher for EMG. The acid dissociation constants are about the same for EMG and DMG, but EMG is more soluble in water than DMG (13.2 and 5.0 mmoles/l, respectively). The UV spectra of EMG and DMG are very similar. © 1968.