Quantitative nmr spectrometry of phase-transfer catalysts. Part 2. Formate Selective Extraction Constants

Selective extraction constants (K_ex(s)) of aqueous sodium formate in the presence of organic solvents and tetraalkylammonium salts were obtained by 300-MHz n.m.r. measurements; data are given for two-phase liquid systems containing chloroform and tetra-butyl-, -hexyl-, -heptyl-, -octyl-, and -dodecylammonium bromides. The values decrease with an increase in the alkyl chain length. The dependence of K_ex(s) on formate concentration was studied in a water-dichloromethane system. Bromide, chloride and sulfate ions were found to have greater affinities than formate for the extracting quaternary ammonium cations.