Anuja, E V; Girish Kumar, K(Cochin University Of Science And Technology, August 6, 2015)
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Abstract:
There is an enormous demand for chemical sensors in many areas and disciplines including chemistry, biology, clinical analysis, environmental science. Chemical sensing refers to the continuous monitoring of the presence of chemical species and is a rapidly developing field of science and technology. They are analytical devices which transform chemical information generating from a reaction of the analyte into an measurable signal. Due to their high selectivity, sensitivity, fast response and low cost, electrochemical and fluorescent sensors have attracted great interest among the researchers in various fields.
Development of four electrochemical sensors and three fluorescent sensors for food additives and neurotransmitters are presented in the thesis. Based on the excellent properties of multi walled carbon nanotube (MWCNT), poly (L-cysteine) and gold nanoparticles (AuNP) four voltammetric sensors were developed for various food additives like propyl gallate, allura red and sunset yellow. Nanosized fluorescent probes including gold nanoclusters (AuNCs) and CdS quantum dots (QDs) were used for the fluorescent sensing of butylated hydroxyanisole, dopamine and norepinephrine.
A total of seven sensors including four electrochemical sensors and three fluorescence sensors have been developed for food additives and neurotransmitters.
The thesis entitled novel heterocyclic constructions mediated by nucleophilic carbenes and related chemistry, embodies the results of the investigations carried out to explore the reactivity patterns of the 1:1 zwitterions, generated in situ from various nucleophilic carbenes and DiMethyl AcetyleneDicarboxylate(DMAD) towards aldehydes and ketones. The traditional synthesis of complex organic molecules employs stepwise formation of bonds and involves multiple steps. Besides the sequential synthesis, in several instances, the desired product can also be obtained in one pot reactions of three or more starting compounds. Such reactions in which more than two starting materials react to form a product in such a way that the majority of the atoms of the starting materials can be found in the products are called multicomponent reactions(MCRs). The results of our investigations on the application of N-heterocyclic carbenes in multicomponent reaction with DMAD and aromatic aldehydes leading to the one pot synthesis of 2-oxy-maleate and furanone derivatives. It is interesting to note that dihydrofuran and lactone motifs are present in a number of biologically active natural products and other heterocyclic compounds. It is conceivable that the novel multicomponent reactions described herein will find application in the synthesis of a variety of heterocyclic compounds, and in natural product synthesis.
Bijumon, P V; Dr.Sebastian, M T; Mohanan, P(Regional Research Laboratory (CSIR), August , 2005)
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Abstract:
This thesis presents the microwave dielectric properties of two novel dielectric
resonator materials with the composition Ca(Ca1/4Nb2/4Ti1/4)O3 and Ca(Ca1/4Ta2/4Ti1/4)O3
ceramics and their application in the fabrication of wideband antennas. The microwave
dielectric properties of the ceramics were tailored by several techniques such as doping,
glass addition and solid solution formations in the complex perovskite A and B-sites with
suitable substitutions. Among the wide variety of DRs developed, ceramic resonators
with optimum properties were identified to fabricate broadband dielectric resonator
loaded microstrip patch antennas. Furthermore, wideband, high permittivity dielectric
resonator antennas were fabricated and explored the possibility of tuning their
characteristics by modifying the feed line geometries.
Deepa, Puthanparambil; Dr. Jayakannan, M(National Institute for Interdisciplinary Science and Technology(CSIR), February , 2008)
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Abstract:
In this introduction part, importance has been given to the elastomeric
properties of polyurethanes. Emphasis has been laid to this property based on
microphase separation and how this could be modified by modifying the segment
lengths, as well as the structure of the segments. Implication was also made on the
mechanical and thermal properties of these copolymers based on various analytical
methods usually used for characterization of polymers. A brief overview of the
challenges faced by the polyurethane chemistry was also done, pointing to the fact
that though polyurethane industry is more than 75 years old, still a lot of questions
remain unanswered, that too mostly in the synthesis of polyurethanes. A major
challenge in this industry is the utilization of more environmental friendly “Green
Chemistry Routes” for the synthesis of polyurethanes which are devoid of any
isocyanates or harsh solvents.The research work in this thesis was focused to develop non-isocyanate green
chemical process for polyurethanes and also self-organize the resultant novel
polymers into nano-materials. The thesis was focused on the following three major
aspects:(i) Design and development of novel melt transurethane process for
polyurethanes under non-isocyanate and solvent free melt condition.
(ii) Solvent induced self-organization of the novel cycloaliphatic
polyurethanes prepared by the melt transurethane process into microporous
templates and nano-sized polymeric hexagons and spheres.
(iii) Novel polyurethane-oligophenylenevinylene random block copolymer
nano-materials and their photoluminescence properties.
The second chapter of the thesis gives an elaborate discussion on the “Novel
Melt Transurethane Process ” for the synthesis of polyurethanes under non-isocyanate
and solvent free melt condition. The polycondensation reaction was carried out
between equimolar amounts of a di-urethane monomer and a diol in the presence of a
catalyst under melt condition to produce polyurethanes followed by the removal of
low boiling alcohol from equilibrium. The polymers synthesized through this green
chemical route were found to be soluble (devoid of any cross links), thermally stable and free from any isocyanate entities. The polymerization reaction was confirmed by various analytical techniques with specific references to the extent of reaction which is the main watchful point for any successful polymerization reaction.
The mechanistic aspects of the reaction were another point of consideration for the
novel polymerization route which was successfully dealt with by performing various
model reactions. Since this route was successful enough in synthesizing polyurethanes
with novel structures, they were employed for the solvent induced self-organization
which is an important area of research in the polymer world in the present scenario.
Chapter three mesmerizes the reader with multitudes of morphologies depending upon
the chemical backbone structure of the polyurethane as well as on the nature and
amount of various solvents employed for the self-organization tactics. The rationale
towards these morphologies-“Hydrogen Bonding ” have been systematically probed
by various techniques. These polyurethanes were then tagged with luminescent
0ligo(phenylene vinylene) units and the effects of these OPV blocks on the
morphology of the polyurethanes were analyzed in chapter four. These blocks have
resulted in the formation of novel “Blue Luminescent Balls” which could find various
applications in optoelectronic devices as well as delivery vehicles.
Siji,Thomas; Vijay Nair,G(ORGANIC CHEMISTRY DIVISION REGIONAL RESEARCH LABORATORY (CSIR), December , 2004)
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Abstract:
A systematic investigation of the reactivity and functionalization of two
heterocyclic analogs of triphenylmethane , namely tris(2-thienyl)methane and
tris(2-furyl)methane have been carried out and the results are presented in this
thesis entitled "NOVEL REACTIONS OF TRIS(2-THIENYL)METHANE AND
TRIS(2-FURYL)METHANE.". The history of organic free radicals dates back to Gomberg's monumental discovery of the triphenylmethyl radical in 1900. The heterocyclic analogs of triarylmethane are also interesting from the vantage point of their transformation to the corresponding radicals akin to Gomberg ' s triphenylmethyl radical and also they are prone to further transformation leading to three dimensionally elongated molecules such as dendrimers. Dendritic architectures are one of the most pervasive topologies observed in nature at the macro- and microdimensional length devices. Because of their ability to combine both organic and inorganic compounds and their propensity to either encapsulate or be engineered into unimolecular functional devices , dendrimers are versatile amongst existing nanoscale building blocks and materials.
Sreekanth,A R; Vijay Nair,G(ORGANIC CHEMISTRY DIVISION REGIONAL RESEARCH LABORATORY (CSIR), November , 2002)
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Abstract:
In the thesis entitled " Novel Strategies for Heterocyclic Constructions via 1 ,4-Dipolar Intermediates"Synthesis of a complex organic molecules essentially involves the formation of carbon-carbon and carbon-heteroatom bonds. Various synthetic methods are available for these processes involving ionic, pericyclic and
radical reactions. Among the pericyclic reactions, dipolar cycloaddition reactions, introduced by Huisgen, have emerged as a very powerful tool for heterocyclic construction. Heterocyclic compounds remain an important class of organic molecules due to their natural abundance and remarkable biological activity, thus constituting an intergral part of pharmaceutical industry. In this respect, developing newer synthetic methodology for heterocyclic construction has been an area of immense interest. In recent years, 1,3-dipolar cycloaddition reactions proved to be efficient routes to a wide variety of five membered heterocycles, as attested by their application in the total synthesis of various complex organic molecules. However, the potential application of similar 1,4- dipolar cycloaddition reactions for the construction of six memebered heterocycles remained underexploited. In this context, a systematic investigation of the reactivity of 1,4-dipoles generated from nitrogen heterocycles (pyridine and its analogues) and dimethyl acetylenedicarboxy!ate (DMAD) towards various dipolarophiles has been carried out and the results are embodied.
Anu Jose; G. Vijay Nair(Cochin University of Science and Technology, August 21, 2014)
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Abstract:
Carbon-carbon and carbon-heteroatom bond formations constitute the
central events in organic synthesis. In view of this, much of the research in
organic synthesis has been focused on devising novel and efficient methods for
such bond constructions. In general, polar, pericyclic and radical methodologies
are employed for this purpose. The polar and radical reactions proceed via
reactive intermediates such as carbanions, enols/enolates, enamines, carbocations,
radical cations, radical anions, carbenes, zwitterions etc. In recent years, there has
been enormous interest in the chemistry of zwitterionic species largely from the
standpoint of their applications in multicomponent reactions (MCRs) and
organocatalytic reactions. Zwitterions formed by the addition of nucleophiles to
electrophilic π-systems such as acetylenic esters and azoesters have been the
subject of extensive investigations; their synthetic utility, however, remained
largely unexplored. Investigations in a number of laboratories, including our own,
have shown that zwitterions of the type mentioned above on reaction with
electrophiles give rise to carbo- and heterocyclic products by 1,3- or 1,4-dipolar
cycloadditions. Recently, allenoates, another class of active π-systems were
introduced to this field. Against this background, a systematic investigation of the
reactions of various zwitterions derived from allenoates with different
electrophiles especially 1,2-diones, were carried out. The results of these studies
are embodied in the thesis entitled “Novel Synthesis of Carbocycles and
Heterocycles Employing Zwitterions Derived from Allenic Esters”.
Rakesh N.; Dr. Prathapan S.(Cochin University of Science and Technology, December 13, 2015)
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Nitrones or azomethine-N-oxides are important precursors for the synthesis of several heterocyclic systems. They belong to the allyl anion type 1,3-dipoles and possess unique structural features which make them extraordinarily useful synthons. They behave as 1,3-dipoles in 1,3-dipolar cycloaddition reactions and as electrophiles in reactions with organometallic reagents. These are the two basic reactions given by nitrones. Nitrones also act as ‘spin traps’ in which they react with short-lived radicals to furnish stable nitroxide radicals which can be detected and identified by electron paramagnetic resonance (EPR) spectroscopy. Recently SmI2 catalysed reductive cross-coupling reactions of nitrones have gained significant interest in which the reactions are initiated by single electron transfer (SET) to nitrones. Apart from these reactions, nitrones are also known to participate in reactions which are initiated by the nucleophilic attack of nitrone-oxygen. In our group, we have also explored the nucleophilic character of nitrones through various reactions. The results obtained enabled us to develop a novel two-step one-pot strategy for quinolines and indoles - the heterocycles renowned for their pharmacological applications, from nitrones and electron deficient acetylenes. Using dibenzoylacetylene and phenylbenzoylacetylene as dipolarophiles, we could introduce a desired functional group at a predetermined position of the quinolines or indoles to be synthesised. In this context, the thesis entitled “NUCLEOPHILIC ADDITION OF NITRONES TO ELECTRON DEFICIENT ACETYLENES AND RELATED STUDIES” portrays our attempt to expand the scope of our
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novel synthetic protocol using ester functionalised acetylenes: dimethyl acetylenedicarboxylate (DMAD) and methyl propiolate.
The thesis is organised in to five chapters. The first chapter briefly describes the different classes of reactions that nitrone functionality can tolerate. The research problem is defined at the end of this chapter. The second chapter describes the synthesis of different nitrones used for the present study. The optimisation and expansion of scope of the novel strategy towards quinoline synthesis is discussed in the third chapter. The fourth chapter portrays the synthesis of indole-3-carboxylates using the novel strategy. In the fifth chapter, the reaction of N-(2,6-dimethylphenyl) and N-(2,4,6-trimethylphenyl)nitrones are discussed. Here we also discuss the mechanistic reinvestigation of Baldwin’s proposal in the isoxazoline-oxazoline rearrangement. The major outcome of the work is given at the end of the thesis.
The structural formulae, schemes, tables and figures are numbered chapter-wise since each chapter of the thesis is organized as an independent unit. All new compounds (except two compounds reported in fourth chapter) are fully characterised on the basis of spectral and analytical data and single crystal X-ray analysis on representative examples. Relevant references are included at the end of individual chapters.
Deepa, Balakrishnan S; Dr.Nandakumar, C G(Cochin University of Science and Technology, January , 2008)
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Abstract:
Frames are the most widely used structural system for multistorey
buildings. A building frame is a three dimensional discrete structure consisting of
a number of high rise bays in two directions at right angles to each other in the
vertical plane. Multistorey frames are a three dimensional lattice structure which
are statically indeterminate. Frames sustain gravity loads and resist lateral forces
acting on it.
India lies at the north westem end of the Indo-Australian tectonic plate and
is identified as an active tectonic area. Under horizontal shaking of the ground,
horizontal inertial forces are generated at the floor levels of a multistorey frame.
These lateral inertia forces are transferred by the floor slab to the beams,
subsequently to the columns and finally to the soil through the foundation system.
There are many parameters that affect the response of a structure to ground
excitations such as, shape, size and geometry of the structure, type of foundation,
soil characteristics etc. The Soil Structure Interaction (SS1) effects refer to the
influence of the supporting soil medium on the behavior of the structure when it
is subjected to different types of loads.
Interaction between the structure and its supporting foundation and soil,
which is a complete system, has been modeled with finite elements. Numerical
investigations have been carried out on a four bay, twelve storeyed regular
multistorey frame considering depth of fixity at ground level, at characteristic
depth of pile and at full depth. Soil structure interaction effects have been studied
by considering two models for soil viz., discrete and continuum. Linear static
analysis has been conducted to study the interaction effects under static load.
Free vibration analysis and further shock spectrum analysis has been conducted to
study the interaction effects under time dependent loads. The study has been
extended to four types of soil viz., laterite, sand, alluvium and layered.The structural responses evaluated in the finite element analysis are
bending moment, shear force and axial force for columns, and bending moment
and shear force for beams. These responses increase with increase in the founding
depth; however these responses show minimal increase beyond the characteristic
length of pile. When the soil structure interaction effects are incorporated in the
analysis, the aforesaid responses of the frame increases upto the characteristic
depth and decreases when the frame has been analysed for the full depth. It has
been observed that shock spectrum analysis gives wide variation of responses in
the frame compared to linear elastic analysis. Both increase and decrease in
responses have been observed in the interior storeys. The good congruence shown
by the two finite element models viz., discrete and continuum in linear static
analysis has been absent in shock spectrum analysis.
Description:
Department of Ship Technology,
Cochin University of Science &
Technology