SPECIFIC AND NONSPECIFIC INTERACTIONS OF HYDROPSEUDOHALIC ACIDS WITH WATER AND ORGANIC-SOLVENTS

Partition coefficients P of the HNCS, HNCO and HN3 hydropseudohalic ac ids between a number of organic solvents and water were determined. It has been found that log P increases with pKa of the acid and with the basicity of the solvent, but the effect of pKa on P is the smaller th e more basic is the solvent. The relationships have been explained in terms of hydrogen bond formation between undissociated acid and solven t molecules. H-bonding between the pseudohalic acids and organic solve nts has been confirmed by IR spectra on the example of HN3 in benzene. Association constants for H-bonding between the three acids and water , benzene, dibutyl ether and tri-n-butyl phosphate were determined fro m partition data. It has been found that H-bonding increases with the strength of the acid, whereas the contribution to partition from non-s pecific interactions with water and organic solvents depends on the mo lecular surface area of the acid molecule.