Please use this identifier to cite or link to this item: http://localhost:8081/xmlui/handle/123456789/1156
Authors: Agarwal, Anita
Issue Date: 1984
Abstract: Nitrogen heterocycles are widely distributed in nature, and are essential to life in various ways. Several of the biologically important compounds contain heterocy clic rings. For example, nucleic acids, vitamins and alkaloids possess a heterocyclic moiety in their structure. The heterocyclic units containing nitrogen and/or any other hetero atom are also present in several antibiotics, aminoacids and enzymes. In view of the great importance of nitrogen and sulfur containing heterocyclic compounds, studies on synthesis and electrochemical behaviour of some of these compounds are reported in this thesis. Electro chemical studies utilised dropping mercury electrode and rough pyrolytic graphite electrode using polarograohy, linear and cyclic sweep voltammetry and coulometric tech niques. The sequence analysis of intact arachin, a peanut protein, and one of its sub-unit was also carried out using manual Edman degradation. Chapter-II describes the synthesis and characteri zation of some N-ohenyl-N'-2 (4,6-alkyl/aryl-5-substituted Phenylazopyrimidyl) thiocarbamides. The synthesis was carried out by the reaction of 2-amino-4,6-dimethyl-5-arylazopyrimidine; 2-amino-4-methyl-6-phenyl-5-arylazopyrimidine and 2-amino-4,6-diohenyl-5-arylazopyrimidine with ii phenylisothiocyanate. The former were synthesised by the action of guanidine nitrate on the reaction product of substituted benzenediazoniumchloride with aryl/alkyl 2,4- diones. The structure of these compounds were confirmed on the basis of elemental analysis, I.K., HNMR and mass spectral studies. The next chapter deals with the electrochemical investigation of some antibacterial compounds obtained by the coupling of sulfadrugs with 1,3-dimethylbarbituric acid. Eight sulfadrugs were coupled with 1,3-dimethylbar bituric acid to give corresponding 5-(p-sulfamoylphenylhydrazono)- l,3-dimethylbarbituric acid derivatives. The electrochemical reduction of these compounds was studied at dropping mercury electrode and pyrolytic graphite electrode using linear and cyclic sweep voltammetry, polarography and coulometry. All these compounds gave well defined, single four-electron transfer irreversible reduc tion wave. The value of an was calculated by log plots [E vs log t^—r - 0.546 log tj and by the method of Oldham and Perry using expression: E t _E. &&£2 log ? X (3-X) bl/2 fc an y 5(1-X) The values calculated by both the methods are in good agreement. In linear and cyclic sweep voltammetry, peak Ill potential (E ) was dependent on pH and shifted towards more negative potential with increase in pri. The number of elect rons, determined by coulometry using mercury pool electrode or graphite electrode was found to be close to four for all these compounds. On the basis of product identification, a plausible mechanism for the reduction has been suggested. The aromaticity and basicity of heterocyclic rings should effect the E-, /2 and E values, riowever, it is observed that as the substituents are remote from the reaction centre, their effect is very small. The electrochemical behaviour of copper complex of 5,5-dimethyl cyclohexane-2-phenylhydrazono-l,3-dione is presented in Chapter-IV. Polarographic and voltammetric reduction of 5,5-dimethylcyclohexane-2-phenylhydrazono-l,3- dione and its copper complex occured in a single 4e, pri dependent step. The half wave potential shifted towards more negative potential with increase in pri. The plot of ^1/2 vs P^ Was Hnear anc* follows the relation -Ew2(pH 3.0-11.4) - [0.072pH + 0.16JV for copper complex. For ligand the variation of Ej/2 with pH observed the relation -E1/2(pri 3.0-11.4) = [0.072pri + 0.17JV Linear and cyclic sweep voltammetry of copper complex at iv rough pyrolytic graphite electrode showed one well defined pri dependent reduction peak. The peak potential (E ) was dependent on pri and can be represented as follows. -E = [0.052pri + 0.30JV. In cyclic voltammetry when the direction of sweep is reversed one more peak is observed at positive potentials and can be represented by a linear relation E = [-0.036pri + 0.96]V Controlled potential electrolysis of copper complex and its ligand indicated that four electrons are involved in the reduction. The spectral changes during electrolysis were recorded for the ligand and copper complex and were found to be identical. As the absorbance did not increase at lower or higher wavelength, it was concluded that no intermediate capable of absorbing at higher or lower wave length is generated during electroreduction. The reduction products were identified by gas chromatography and thin layer chromatography. As the ligand and its copper complex indicated an identical behaviour it is concluded that the copper complex is labile and dissociates in the solution to give free ligand and the metal. The last chapter of the tnesis is devoted to the N-terminal sequence analysis of arachin (a peanut protein) V by Edman degradation. Arachin, a protein with molecular weight 3,30,000, was isolated from defatted groundnut powder, purified to homogenity and sequence of first sixty residues of intact arachin was determined. It has been shown that arachin is dissociated into small molecules of low molecular weignts. A sub-unit having molecular weights25000 was isolated from arachin end subjected to manual Edman degradation for determination of complete amino acid sequence. This sub-unit was hydrolysed partially by CNBr and pepsin. The different fragments were separated and purified by gel filtration and electrophoresis. Thus eight fragments (CNj-CNg) were separated from CNBr hydrolysate and eight fragments (Pj_-P8) were separated from pepsin hydrolysate. The residue on the electrophoretogram was eluted in each case and subjected to further electro phoresis at varying conditions. Thus eight fragments (CNRj-CNRg) pertaining to CNBr h/drolysate and six frag ments (PR1-PR6) pertaining to pepsin digest were obtained. Each of these fragments was subjected to complete hydrolysis and manual Edman degradation to determine the complete sequence. Each peptide is overlapped by at least 4 or 5 residues. Thus a sequence of 201 residues was identified in the arachin sub-unit chain. The PTri-amino acids were identified by T.L.C. and \J.V.
Other Identifiers: Ph.D
Research Supervisor/ Guide: Bhushan, Ravi
Goyal, R. N.
metadata.dc.type: Doctoral Thesis
Appears in Collections:DOCTORAL THESES (chemistry)

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