ION-ION AND ION-SOLVENT INTERACTIONS OF LITHIUM PICRATE AND LITHIUM PERCHLORATE IN PURE NITROMETHANE AND IN 15-CROWN-5-DEGREES-C(NITROMETHANE MIXTURES AT 25)

Solutions of LiPi and LiClO4 in nitromethane were studied by conductan ce at 25-degrees-C in the concentration range 0-10(-2) mol l-1. Althou gh the dielectric environment is the same, the conductometric behavior of these two electrolytes is quite different: LiPi is almost non-cond ucting whereas LiClO4 behaves like a normal electrolyte. The analysis of the conductance data gives ion pair association constants of the or der of 10(6) for LiPi and 10(2) for LiClO4. The results are discussed in terms of specific ion-ion and ion-solvent interactions related to t he molecular details of the anions and the solvent molecules. One-to-o ne complexes between 15-crown-5 and the lithium ion were observed, add ing the macrocyclic ligand to the systems. A dramatic increase in the conductance of both electrolytes in the presence of 15-crown-5 was als o observed. The overlap of the complexation process and the ion-pair p rocess is discussed.