College of Science

The work in this thesis involves four parts:

Part one: Synthesis of 2,5-disubstituted-1,3,4-thiadiazoles:

For the synthesis of the titled compounds the following sequence of steps (step -1- to step -8- ) were followed.

Step-1- : Synthesis of 2,5-dimercapto-1,3,4-thiadiazole [1].

It was prepared by cyclization of hydrazine hydrate with carbon disulfide in alkaline medium.

The scheme of this work involves synthesis of different five and six membered heterocyclic rings starting from 4-nitrophenyl hydrazine and two different acid hydrazides (benzoic hydrazide and            p-chlorobenzoic hydrazide) which were synthesized from their carboxylic acids.This work is divided into four different parts:

First part:

      Cephalexin is a medical drug administrated commonly for the treatment of infections.Two methods were examined for determination of cephalexin based on conventional and derivative UV absorption spectrophotometry.The calibration curve at 262 nm has linear range extended from (1.5-100) ppm with relative standard deviations for the slope of 0.91 and correlation coefficient of 0.9993. The effect of pH on the determination of cephalexin at this wavelength was also investigated.