2. Thesis and Dissertations
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Item Synthesis, characterization and studies on antitubercular activity of some 1,3,4-thiadiazole based molecules(National Institute of Technology Karnataka, Surathkal, 2016) Ramprasad, J.; D, Udaya kumarIn the last few decades, the process of drug discovery program has undergone a fundamental transformation, thanks to the integrated approach of chemists and biologists resulting in the development of new chemical entities (NCEs). Although the increasing costs of production, research and development worries the pharmaceutical industry, synthetic organic approach towards designing innovative and low molecular weight chemical structures, which are also biologically active, will definitely aid in combating the ailments prevailing universally. Such endeavours have led us to domain of heterocyclic chemistry and thiadiazole is one such frequently encountered heterocycle which has proven itself with a diverse range of biological activities. Owing to this therapeutic degree of thiadiazole and its derivatives, in the current work, it has been planned to integrate various potent heterocyclic units with the thiadiazole skeleton to form a new molecular framework. Accordingly, five different libraries of thiadiazole based compounds comprising of benzimidazole (T1-T29), 1,2,3-triazole (T30-T49), thiazole (T50-T72), phenothiazine derivatives (T73-T93) and pyrazinamide (T94-T111) have been successfully synthesized through multistep organic synthetic protocols. Derivatives T1-T72 and T93-T111 were synthesized with a pharmacophore substitution at position-5 of imidazo[2,1-b] [1,3,4]thiadiazole ring. Derivatives of T73-T93 were synthesized by the reaction of 1,3,4-thiadiazole core with substituted phenothiazine as the pharmacophore unit. The chemical structures of the prepared molecules were established by various spectroscopic techniques viz. 1H NMR, 13C NMR, ESI-MS and elemental analyses. Additionally, 3-dimensional structures of a few molecules were confirmed by single crystal X-ray diffraction (SCXRD) studies. Further, the synthesized title compounds were subjected to preliminary in vitro antitubercular and antibacterial screening. The active molecules in each series were identified and tested for their toxicity on the benign noncancerous cells. The in silico molecular modeling studies of these active derivatives were also carried out.Item Effect of T6 Heat Treatment on Corrosion of Al-SiC p Composite & Inhibition Evaluation of Benzimidazole & Its Derivatives(National Institute of Technology Karnataka, Surathkal, 2017) Chacko, Melby; Nayak, JagannathaAluminium alloys, particularly 6061, reinforced with SiC have been the focus of the attention because of their application potential in an extensive range of demanding applications, such as automobiles, aerospace, and defense. There are many other applications which involve exposure of the composites to the potential corrosive environment. Because of the duplex nature of the composites, they are prone to accelerated corrosion compared to their monolithic counterpart. Corrosion of these composites not only limit their service life but also lead to deterioration of their unique mechanical properties for which they are designed. Studies reveal the role of micro structural changes and processing routes on the corrosion behaviour. Also, aging treatment was found to have an influence on the corrosion rate as the heat treated samples showed higher corrosion rates as compared to the non-treated samples. Corrosion studies in organic acid solutions are rare in comparison with similar studies in mineral acids. Acetic acid is a frequently used organic acid in many industrial processes. At high temperatures, these acids dissociate, generating new aggressive ions which cause faster corrosion and they can provide sufficient protons to act as true acids. Adding inhibitors to the corrosion medium is a general practice for the corrosion protection. Heterocyclic organic compounds which contain oxygen, sulphur, phosphorous, nitrogen and aromatic rings are considered to be the most active and resourceful inhibitors in the acidic corrosive medium for the metals, alloys, and composites. Latterly, benzimidazole and its derivatives have established a considerable reputation on their corrosion inhibition properties for metals and alloys, owing to the existence of aromatic rings and nitrogen atom. In the present study benzimidazole (BI), 2-methylbenzimidazole (2-CH3-BI), and 2- mercaptobenzimidazole (2-SH-BI) are used as inhibitors. Aging profile of T4 and T6 treated Al-SiCp was obtained using Rockwell B hardness. Under-aging, peak-aging, and over-aging temperatures and time were found out. Samples were corrosion tested and found to be susceptible to corrosion in acetic acid where peak-aged samples exhibited higher corrosion and over-aged samples8 showed minimum corrosion. Three inhibitors were tested for their efficiency. Results proved that they are excellent inhibitors. The maximum inhibition efficiency obtained using BI was 66%, 69% offered by 2-CH3-BI and 75% was achieved in the presence of 2-SH-BI. Inhibition efficiency of inhibitors followed the order of 2-SH-BI > 2- CH3-BI > BI. Activation energy, enthalpy, entropy, and free energy of adsorption were calculated for all experimental conditions. Results suggest that inhibitors get adsorbed on the composite surface by mixed adsorption, where chemisorption is predominant.Item Synthesis of Some New Pyrazole Derivatives and Their Antituberculosis Screening(National Institute of Technology Karnataka, Surathkal, 2017) Nandam, Harikrishna; Isloor, Arun M.Antibiotics improve the better living life in the world for human as well as animals. Many types of bacteria are dramatically reduces illnesses and deaths caused by various infections. Therefore, it occupies great importance to discover newer, effective and safer drugs in the modern world. In the last few decades, the process of drug discovery program has undergone fundamental transformation to synthesize customs molecules and new chemical entities (NCEs). Organic synthesis approaches towards designing, innovation and low molecular chemical structures, which are easily available, biologically active, will definitely aid in combating the ailments prevailing universally. Although, the increasing cost for discovery of such molecules in terms of research and development, analysis, in vitro and in vivo studies for new sites were worries the pharmaceutical research. Newer heterocyclic compounds are being employed constantly in the hope of striking a proper perspective in combating the pathogen bacterial infections. A systemic investigation of this class of heterocyclic lead revealed that, pyrazole and its derivatives are well known nitrogen containing heterocyclic compounds occupy an important role in medicinal chemistry with wide variety of biological properties. Owing to this therapeutic degree of pyrazole and its derivatives, in the current research work, it has been planned to find out various potent heterocyclic moieties with pyrazole through active functional systems to form a new molecular framework. Accordingly, different libraries of pyrazole based compounds comprising of thiazole (T1-12), pyrazoline (T13-27), 1,4-dihydropyridine (T28-45), 1,3,4-oxadiazole (T46-54), [1,2,4]triazolo[3,4-b] [1,3,4]thiadiazole (T55-63), benzimidazole (T64-79) and trifluoromethylbenzyloxy derivatives (T80-97) have been designed and synthesized. Newly synthesized chemical derivatives were confirmed by various spectroscopic techniques viz. FT-IR, 1H-NMR, 13C-NMR, LC-MS and elemental analyses. Additionally, three dimension structures of few molecules were confirmed by single crystal X-ray diffraction (S-XRD) studies. Further, the target compounds were subjected to screen preliminary in vitro antitubercular, antibacterial and antifungal activities. The active molecules were identified and tested for their cytotoxicity studies against non-cancerous cells.