Spectrophotometric determination of captopril in dosage form via charge-transfer complexes

Two simple and sensitive spectrophotometric methods for the assay of captopril have been presented. The first is based on the reaction of captopril with iodine to give a molecular charge-transfer complex. The second method depends on the formation of a highly colored stable radical anion between captopril and 7,7,8,8-tetracyanoquinodimethane [TCNQ] as a pi-electron acceptor. The molecular ratios of the reactants in the complexes as well as the experimental conditions leading to maximum charge-transfer b and s have been studied. Beer's Law is obeyed over captopril concentration range of 2-8 mug.ml -1 by iodine method and 0.32-3.2 mug.ml -1 by TCNQ method. The proposed procedures have been applied successfully to the analysis of captopril tablets and the results are in agreement with those of official methods

reaction of 3- [2-thienyl] -5-mercapto-4H-1,2,4-triazole with aralkyl halides

The reaction of 3-[2-thienyl]-5-substituted mercapto-4H-1,2,4-triazoles 7a-c with benzyl bromide yielded a separable mixture of 3-[2-thienyl]-4- benzyl-5-substituted mercapto-1,2,4-triazoles 4a-c and 1-benzyl-3-[2-thienyl]-5-substituted mercapto-1,2,4-triazoles 8a-c. This was confirmed by independent synthesis of 4a-c through the reaction of 3-[2-thienyl]-4-benzyl-5-mercapto-1,2,4-triazole 3 with the appropriate aralkyl halide in the presence of sodium methoxide