Collect. Czech. Chem. Commun. 1993, 58, 783-790

Conductometric Studies of Molecular Complexes of Charge Transfer Type Formed between Aza-Aromatics and Haloanils

Harbhajan S. Randhawa and Rajni Lakhani

Department of Chemistry, Punjab Agricultural University, Ludhiana-141 004, India


Electrical conductivity technique has been employed to investigate the molecular interaction of aza-aromatics viz. pyridine, α-pikoline, β-picoline and γ-picoline with haloanils, namely chloranil, bromanil and fluranil. The stoichiometry of the charge transfer (CT) complexes has been established and molar conductivities of the complexes determined employing the method of Gutmann and Keyzer. A model has been proposed for determining the equilibrium constant (K) of 1 : 1 molecular complexes of CT type by conductometric measurements. The model involves the assumption: 1/σ = [(1 + K c0A)/qdK c0A] (1/c0D) + (1/qd c0A), where σ is the conductivity of the molecular complex, qd is the extent of depolarization of the complex, c0A) and c0D) are the initial concentrations of the acceptors and donors, respectively. The values of K and qd follows the expected trend of the conductometric parameters determined by the method of Gutmann and Keyzer as well as ionization potential of donors, thereby substantiating the validity of the model proposed. The observed and theoretical values of thermodynamic parameters for the aza-aromatic-chloranil systems that the interaction of aza-aromatics with haloanils is occurring through the lone pair of nitrogen ring.