ELECTROCHEMICAL AND OPTICAL PROPERTIES OF SOME PYRIDINYL COMPOUNDELECTROCHEMICAL AND OPTICAL PROPERTIES OF SOME PYRIDINYL COMPOUND

Abstract

In order to gain information regarding the structure of charge transfer complex l - ethyl - 4 - carbomethoxy pyridinium iodide (PyI ) and to investigate the situation of i on- pairing, some proton magnetic resonance and conductance studies were carried out in various sol vents. Proton magnetic resonance studies were extended to study the exchange reactions between PyI and Py CI04 , and between pyridinium salt and tetra-butyl ammonium salts . shifts It was noted that proton chemical ~rising from aromatic protons of salt under investigation were solvent dependent, and a correlation seems :tID /exist between the solvent polarity parameter Z- value and chemical shift values of aromatic protons . The~& values were h i ghest in chloroformb S- = 1.17; (Z = 63.2) and lowest in H2 () ~ &- = 0.57 (Z = 94.6). An. interesting phenomenon was ob served during the cour se of study of exchange reactions between PyI and Py CI04 also, between Py GI04 and TBAI, was that instead of having two set of r esonance lines, one for each PyI and PyCI04 , rather only one set~s observed. It was concluded that there was extremely rapid exchange between iodide and perchlorate ion. The conductance studies were carried out to investigate the ionpairing phonomena and also effect of change of temperature and solvent polarity on the ion-pair dissociation constant. The magnitude of K was of the order of 10- 2 to 10 - 3 as , which suggested that pyridinium iodide exists essentially/ i on-pairs. In different solvents under the similar conditions of temperature it was noted that ion -pair dissociation constant value decreases with the decrease in solvent polarity (die lectric constant 8). It has been observed for a particular solvent that the K value increases with the rise in temperature. It \"as concluded that both temperature and dielectric constant of the solvent, affect the ion- pairing, such that the latter phenomenon is unfavoured by the increase in temperature or dielectric constant v value of the solvent . Conductance studies were also carried out in CHC13 solvent but conductance data obtained showed variation , thus it was not possible to calculate the value of K and ~o from the experimental data. log ~c Vs. log c plots exhibited a minima, and it was concluded that triplet ions (py+r-py+ and r-py+r-) may be existing.