Abstract
Abstract The stability constants and thermodynamic functions for 1:1 adduct formation of unidentate heterocyclic bases with copper(II) β-diketonates were determined in non-aqueous solvents by the spectrophotometric method. The main factors controlling the stability of the adducts were investigated and the bases were classified into two groups in adduct formation from the plots of the stability constants against pKH values of the bases: steric hindered and unhindered bases. Large negative entropy changes were observed for pyridine, β-picoline, and γ-picoline; these were ascribed to the π-bond character of the adduct bonds. A solvent effect was observed; the order of increasing adduct stability was as follows: acetone <butyl acetate <4-methyl-2-pentanone <chloroform <nitrobenzene <toluene \simeq benzene <chlorobenzene. This order agreed with the decreasing order of the solvent-chelate interaction and of the solvent-base interaction. In all cases, the adducts were stabilized by large exothermic enthalpy changes. Moreover, the introduction of a CF3 group into β-diketones also brought about a considerable entropy change which promoted the stabilization of the chelate. The effect of the other terminal groups was not clearly observed.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.