Abstract
The reactions between diphrenhydramine drug (diphen) in the base form and the iodine amphoteric reagent (n-donor and/or σ-acceptor) and tetracyanoethylene as a π-acceptor reagent (TCNE) have been spectrophotometrically studied at different conditions of reactant concentrations, time intervals, temperatures, solvents, and different wavelengths aiming to shed light on the nature of these reactions. Consequently, it is possible to select the proper conditions for spectrophotometric determination of this biologically active drug in its formulations. The reaction mechanism between iodine and diphen involves the formation of diphen-I₂ outer-and inner-sphere complexes, whereas diphen-TCNE reaction involves the formation of charge transfer (CT) complex. The analytical parameters of the suggested spectrphometric procedures have been calculated. The values of the Sandell sensitivity, standard deviation (SD), relative standard deviation (RSD) and recovery % refer to the high sensitivity of these procedures applied in analysis of diphen in its formulations. This research also presents a new diphen-I₂ promising drug derivative that can be used for the same purpose as its parent. Both diphen-drug and diphen-I₂ separated solid product are critically investigated by elemental analyses, FT-IR, ¹HNMR, electron ionization mass spectrometry (EI-MS) and thermal analyses (TA). Practical investigation (TA and MS) data of diphen-drug and its reaction product are confirmed by MO calculations. This research gives a clear idea about the possible metabolites and metabolic pathways of diphen and its derivative in vitro system that may occur in vivo system. The importance of this drug stems from its use as an antihistamine with anticholinergic (drying) and sedative side effects.