HYDROGEN-BONDING - PART 44 - THERMODYNAMICS OF COMPLEXATION OF 3,5-DICHLOROPHENOL WITH KETONES AND ETHERS IN CYCLOHEXANE - THE BADGER-BAUERRELATIONSHIP

Equilibrium constants for 1:1 hydrogen bond complexation between 3,5-d ichlorophenol (DCP) and 17 ketones and 12 ethers in cyclohexane soluti on have been obtained by an FTIR method that takes into account both d imerization of the acid and formation of 2:1 complexes. Enthalpies of complexation for the same ketones and ethers have been determined by a calorimetric method, leading to values of log K, Delta G degrees, Del ta H degrees and Delta S degrees for 1:1 complexation in the 29 system s, as well as log K-2 for the 2.1 complexation between 2 mol of acid a nd 1 mol of base. For the ketone systems there is very little variatio n in the three thermodynamic parameters with alkyl substitution, but f or the ethers there are systematic variations depending on the alkyl s ubstituent or if the ethers are cyclic. Values of the OH stretching fr equency in the DCP complexes with the ketones and ethers in cyclohexan e have been obtained. The band shapes for the DCP-ketone complexes are very asymmetric, possibly due to the presence of stereoisomeric compl exes, but the v(OH) band for DCP-ether complexes is symmetric and very suitable for the evaluation of any relationship between v(OH) and Del ta H degrees. It is found that for the complexation of DCP with the 12 aliphatic ethers in cyclohexane, there is almost no connection betwee n the calorimetrically determined Delta H degrees values and values of Delta v(OH).