Please use this identifier to cite or link to this item: http://localhost:8081/xmlui/handle/123456789/1178
Authors: Minocha, Ashwani Kumar
Issue Date: 1985
Abstract: Nitrogen and sulphur containing compounds of medicinal and physiological importance have been the subject matter of basic research for the last many decades. Early studies were mostly centred on their synthesis and characterisation, but in later years more critical and comprehensive studies dealing with their spectral properties and redox behaviour were undertaken. Thiazole derivatives are of considerable interest from therapeutic point of view, because of their wide spectrum of activity. The toxic nature of thiazoles has been found to be diminish and completely lost in the presence of some substituents Various thiazoles derivatives have been used in cancer and diabetic research and few of them have shown remarkable activity against these diseases. In recent years thiazoles possessing arylazo moiety have been found effective for antineoplastic activity. This interest stems mainly from carcinostatic activity of heterocyclic carboxaldehyde, semicarbazones, thiosemicarbazones, hydrazones and interfering action of arylazo grouping with nucleic acid synthesis. In view of remarkable activity of thiazoles a research plan was developed to synthesise a varieties of thiazoles bearing arylazo grouping at appropriate position. As thioureido linkage is also of considerable importance in increasing the ii biological activity of the molecules, it was introduced at suitable position in the expectation that these compounds will exhibit significant activity. The electrochemical behaviour of biologically important compounds provides a unique and valuable insight into the biological redox reaction of these molecules. A large number of biologically important compounds have been studied by polarography or other related techniques. The polarographic studies have not only provided useful information about the redox mechanism of these compounds but also brought out clearly the utility of polarographic method in elucidating the structure of these compounds. In some instances it has been demonstrated that electrochemical investigations reveal the path of enzymic oxidation of purines and their nucleosides. The electrochemical behaviour of some important class of hydrazones and semicarba zones, which are frequently used as intermediates in the synthesis of biologically important compounds particularly arylazothiazoles were studied to get information about their redox-behaviour at dropping mercury electrode and at rough pyrolytic graphite electrode. The thesis describes the following aspects of biologically important compounds. Chapter I« General Introduction Chapter II. Synthesis and characterization of some 2-Amino- 4-aryl-*5-(p~azobenzene sulphon-amido) thiazoles as possible antibacterials. Ill Chapter III. Synthesis and characterization of some N-phenyl- N»_[4-aryi-5(N-substituted sulphamidoazo) thiazol- 2yl] thiocarbamides as possible antibacterial compounds. Synthesis of N-phenyl-N'-(4-aryl-5(N-substituted sulphamidoazo) thiazol-2-yl] thiocarbamides was achieved in two steps. In the first step diazotisation of appropriate sulphadrug and its coupling with 2-amino-4arylthiazoles gave 2-amino-4-aryl-5-pbenzene sulphonamylazothiazole. In second step amino group at position-2 was allowed to react with phenyl isothiocynate to give the desired compounds with azo group and thioureido moiety. These compounds have been characterised by elemental analysis, IR and mass spectral studies. S -r—N = N~T_y-S02NHR <Q>-NH -C-HN^^-<ytR S <*> Chapter IV. Electrochemical Behaviour of copper^compter of 2,3,4-pentanetrione-3-phenylhydrazone. This chapter describes the electrochemical behaviour of 2,3,4-pentanetjrione~3-phenylhydrazone and its copper complex using polarography, linear and cyclic sweep voltammetry coulometry and related techniques. Both ligand and its copper complex reduced in a single, pH-dependent, well defined iv 4-electron step in the pH range 3.0 to 11.2. The linear plot of i , vs V"n and low values of temperature coefficient (below 1.8^ deg"" ) indicated the diffusion controlled nature of the limiting current. The plots of -E, /2 vs pH and -E vs pH were linear for copper complex but showed a break around pH 9.0 for ligand. The product identification by gas-chromatography clearly indicated that electro reduction of ligand and copper complex give different products. Chapter V. Elucidation of Redox Behaviour ?f Ethyl 2,3-dioxobutyrate 2~phenylhydrazono-3-9emicarbazone by polarographic and voltametric techniques. From the polarographic point of view semicarbazones resembles with hydrazones. Due to the great importance of semicarbazones, this investigation was initiated in the expectation that a comparison of electrochemical behaviour of ethyl 2,3-dioxobutyrate-2-phenylhydrazone-3-semicarbazone (II) with possess two polarographically reducible sites, viz, hydrazono and semicarbazono with ethyl 3-oxobutyrate semicarbazone (III) will throw some light on the biological redoxreaction of this molecule. Tj\-NH -N=» c; (II) .C00C2H5 N.NHCONH, H2CX COOC2H5 C - CH, H 3 N.NH.CONH, (III) The electrochemical characteristics of these compounds *re summarised below: I) II) Compound (II) reduced in a single 4 electron transfer, diffusion controlled, irreversible wave. The -B / and ~E were found t0 be pH dePendent and variation of -E with pH observed the relationship _E = [0.055pH + 0.38] V P III) In cyclic voltammetry at a scan rate of 200 mVs an anodic peak 11 was also observed in the reverse sweep. Chapter VI. Electrochemical behaviour of bisazo dye- Direct Red 81. Aromatic azo compounds constitute a well known and highly important class of compounds from both theorotical and practical point of view. The electrochemical behaviour of azo compounds substituted with another azo group has attracted little attention. In this chapter electrochemical investigation of Direct Red 81, a bisazodye (IV) have been carried out at dropping mercury electrode and pyrolytic graphite electrode using polarography, linear and cyclic sweep voltametry, coulometry and other related techniques. -Na03s f=rN H-GO -f~^) NaO (IV) VI The polarographic reduction of Direct Red 81 occured in two well defined waves in the pH range 3.0-9.2. In pH range 3.0-4.6, first wave was found 2e process and second wave was 6e process. With increasing pH the height of the first wave decreased and at pH 6.0 the limiting current of both the waves become equal. In the pH range 9.3 to 11.2 the first 4e wave was splitted into two 2e waves. The waves were found to be diffusion controlled and showed a pH dependent nature. Cyclic sweep voltammetry gives two peak 1 and llc. After scanning peak 11 when the direction of the sweep is reversed an anodic peak 111 is observed, which forms an almost irreversible couple with peak 111 on the subsequent sweep towards negative potential. By initiating the sweep in positive direction first, no anodic peak (111 ) was observed. Also if the direction of sweep is changed after recording peak 1 the couple lllg and 111 was not observed. Thus it is confirmed that couple 111 c and 111 can be seen only after complete electroreduction of c dye. The end products of electroreduction have been character ized and a reduction mechanism has been proposed on the basis of products identification and number of electrons involved in the reduction.
Other Identifiers: Ph.D
Research Supervisor/ Guide: Goyal, R. N.
Srivastava, S. P.
metadata.dc.type: Doctoral Thesis
Appears in Collections:DOCTORAL THESES (chemistry)

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