Intramolecular Hydrophobic Association of Two Alkyl Chains of Oligoethylene Glycol Diethers and Diesters in Water

Article abstract of DOI:10.1021/j150668a009

The octanol-water partition coefficients P of C_nH_2n+1O(CH2CH2O)_mC_nH_2n+1 and C_nH_2n+1COOCH2CH2OCOC_nH_2n+1 are measured and analized on the basis of an empirical linearity between cavity surface area S and hydrophobicity.The slope a of log P vs. total alkyl chain length n_t plots of these double chain compounds is smaller than that, a_I, of oligoethylene glycol monoethers.The slope of log P vs. m plots at constant n is dependent on n and m for these diethers but is independent of n and m for the monoethers.These facts suggest that two alkyl chains of the diethers associate intramolecularly in water.As the distance d between two alkyl chains in the all-trans arrangement decreases, S of a solute molecule decreases.On the basis of the above results and the conformations of related compounds, several conformations of diethylene glycol diethers in water can be considered and the most probable conformation of ROCH2CH2OCH2CH2OR is suggested as follows: tggttg'g't.The conformations of ethylene glycol diethers and diesters are also suggested.