Download or read book Studies on the Mechanisms of Decarboxylation of Pyridine and Pyrrole Carboxylic Acids in Aqueous Solution microfilm written by G. K. J. Lee and published by . This book was released on 1970 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Studies on the Mechanisms of Decarboxylation of Pyridine and Pyrrole Carboxylic Acids in Aqueous Solution microform written by Lee, Gordon Kwok-Jung and published by National Library of Canada. This book was released on 1970 with total page 372 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Studies on the Mechanisms of Decarboxylation of Pyridine and Pyrrole Carboxylic Acids in Aqueous Solution microfilm written by G. K. J. Lee and published by . This book was released on 1970 with total page 372 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Mechanisms of Decarboxylation written by Scott Owen Chelmsford Mundle and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 2-(2-mandelyl)thiamin (MTh), the adduct of benzoylformate and thiamin, is an accurate model of 2-(2-mandelyl)thiamin diphosphate, the initial covalent intermediate in the decarboxylation of benzoylformate by benzoylformate decarboxylase (BFDC). The first order rate constant for spontaneous decarboxylation of MTh is about 106 times smaller than the enzymic rate (kcat) for the BFDC reaction. Based on the similarities of MTh and the corresponding enzymic intermediate, as well as the inherent nature of the intermediate, it is not obvious why the enzyme-catalyzed reaction is so much faster. However, earlier studies showed that the decarboxylation of MTh is catalyzed by protonated pyridines and this was proposed to occur through a preassociation mechanism. If this explanation is correct, then the observed 12C/13C kinetic isotope effect (CKIE) will increase in the presence of the catalyst as a more favorable forward commitment is made possible. This provides a specific model for the enzyme-catalyzed process. We developed a technique using headspace analysis and compound specific isotope analysis (CSIA) to determine the CKIE for the decarboxylation of MTh in the presence and absence of pyridinium. We found that the CKIE increases in the presence of the catalyst, as predicted for the preassociation mechanism. In a related study, we investigated the kinetics of decarboxylation of pyrrole-2-carboxylic acid, which was known to be subject to acid catalysis in highly acidic solutions. In the expected mechanism, protonation of the pyrrole ring at C2 destroys the aromaticity of the ring. C-C bond cleavage in the process of decarboxylation will re-establish the aromatic pyrrole. However, the overall reaction rate would not increase as it is counteracted by a larger concentration of the undissociated carboxyl group compared to carboxylate ion necessary for decarboxylation. Since the reaction occurs readily, there must be an alternative pathway for the acid-catalyzed reaction. This can be achieved in an associative mechanism that is initiated by addition of water to the carboxyl group of the carboxyl-protonated reactant. C-C bond cleavage results in formation of pyrrole and protonated carbonic acid, a species that has been recognized as a viable intermediate in related processes. Protonated carbonic acid is spontaneously converted to H3O+ and carbon dioxide. The associative mechanism is consistent with solvent-deuterium kinetic isotope effects and 12C/13C kinetic isotope effects.
Download or read book Quinolone Antibacterials written by Jochen Kuhlmann and published by Springer. This book was released on 2012-02-12 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: It has been over 30 years since the first clinically important member of the quinolone class, nalidixic acid, was introduced into medical practice. The modification produced in the quinolone nucleus by introducing a fluorine at the 6-position led to the discovery of the newer fluoroquinolones with enhanced antibacterial activities as compared to nalidixic acid. By now a great deal of preclinical and clinical experience has been obtained with these agents. The intense interest in this class of antibacterial agents by chemists, micro biologists, toxicologists, pharmacologists, clinical pharmacologists, and clini cians in various disciplines encouraged us to summarize the information on the history, chemistry, mode of action and in vitro properties, kinetics and efficacy in animals, mechanisms of resistance, toxicity, clinical pharmacology, clinical experience, and future prospects in one volume of the Handbook of Experimental Pharmacology. As this series deals predominantly with "experimental" characteristics of drugs, our volume is dedicated specifically to quinolones and emphasizes principally their preclinical and clinical phar macological characteristics, despite the existence of several summaries on quinolones. The chemistry of the quinolones is described in detail. The chapter on the mode of action of quinolones reports the conclusive evidence that gyrase is the intracellular target of the quinolones; however, another enzyme, topoisomerase IV, may also be a target for quinolones, and the exact mechanisms by which quinolones act bactericidally are far from being understood.
Download or read book Organic Pollutants in the Water Cycle written by Thorsten Reemtsma and published by John Wiley & Sons. This book was released on 2006-12-13 with total page 368 pages. Available in PDF, EPUB and Kindle. Book excerpt: This first in-depth and comprehensive reference on the most pertinent polar contaminant classes and their behavior in the whole water cycle includes, among others, industrial chemicals, consumer products, polar herbicides and pharmaceuticals. All chapters are uniformly structured, covering properties, pollution sources, occurrence in wastewater, surface water, and groundwater as well as water treatment aspects, while ecotoxicological and assessment aspects are also covered. Among the authors are leading experts in their relevant fields, many of whom provide here groundbreaking research results. The result is an up-to-date information source for researchers and professionals working in water quality monitoring, water supply, or wastewater treatment, as well as environmental and water chemists, geochemists, ecologists, chemists and engineers.
Download or read book Chemical Biomarkers in Aquatic Ecosystems written by Thomas S. Bianchi and published by Princeton University Press. This book was released on 2011-02-28 with total page 417 pages. Available in PDF, EPUB and Kindle. Book excerpt: This textbook provides a unique and thorough look at the application of chemical biomarkers to aquatic ecosystems. Defining a chemical biomarker as a compound that can be linked to particular sources of organic matter identified in the sediment record, the book indicates that the application of these biomarkers for an understanding of aquatic ecosystems consists of a biogeochemical approach that has been quite successful but underused. This book offers a wide-ranging guide to the broad diversity of these chemical biomarkers, is the first to be structured around the compounds themselves, and examines them in a connected and comprehensive way. This timely book is appropriate for advanced undergraduate and graduate students seeking training in this area; researchers in biochemistry, organic geochemistry, and biogeochemistry; researchers working on aspects of organic cycling in aquatic ecosystems; and paleoceanographers, petroleum geologists, and ecologists. Provides a guide to the broad diversity of chemical biomarkers in aquatic environments The first textbook to be structured around the compounds themselves Describes the structure, biochemical synthesis, analysis, and reactivity of each class of biomarkers Offers a selection of relevant applications to aquatic systems, including lakes, rivers, estuaries, oceans, and paleoenvironments Demonstrates the utility of using organic molecules as tracers of processes occurring in aquatic ecosystems, both modern and ancient
Download or read book Essentials of Biochemistry written by Herbert J. Fromm and published by Springer Science & Business Media. This book was released on 2012-01-05 with total page 380 pages. Available in PDF, EPUB and Kindle. Book excerpt: This textbook, Essentials of Biochemistry is aimed at chemistry and biochemistry undergraduate students and first year biochemistry graduate students. It incorporates the lectures of the authors given to students with a strong chemistry background. An emphasis is placed on metabolism and reaction mechanisms and how they are studied. As the title of the book implies, the text lays the basis for an understanding of the fundamentals of biochemistry.
Download or read book Perspectives in Organic Chemistry written by Alexander Robertus Todd and published by . This book was released on 1956 with total page 550 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Reactive Intermediates written by Leonardo S. Santos and published by John Wiley & Sons. This book was released on 2009-11-04 with total page 341 pages. Available in PDF, EPUB and Kindle. Book excerpt: During the last two decades there has been considerable growth in the development of electrospray ionization mass spectrometry (ESI-MS) as a practical method in the study of reaction mechanisms. This method allows the interception and characterization of key intermediates, either as transient species or as protonated/deprotonated forms of neutral species by API-MS. The outstanding features and advantages of ESI-MS make it one of the most suitable tools for the fast screening of intermediates directly from solution, providing hitherto unavailable chemical information to organic chemists. This monograph provides an overview of the mechanisms involved in ESI-MS, the historical perspectives before looking further in-depth at specific reactions and intermediates. Written by researchers in the field, this book is an unique resource for the understanding of this cutting-edge technique.
Download or read book MCQs in Biochemistry written by G. Vidya Sagar and published by New Age International. This book was released on 2008 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: Medical and Paramedical graduates aspiring for higher education planning to take PG ought to appear in entrance examinations. These entrance examinations are usually patterned in objective type. Biochemistry forms an integral part of curriculum of medical and paramedical courses. It is an important subject and deals with various Chemical, Biochemical, and Physiological reactions and processes that take place inside a living system. Quite a large number of MCQs appear in PG medical and paramedica.
Download or read book Organofluorine Compounds written by Tamejiro Hiyama and published by Springer Science & Business Media. This book was released on 2013-03-09 with total page 281 pages. Available in PDF, EPUB and Kindle. Book excerpt: In view of increasing interest in organofluorine compounds, this book was undertaken to describe biological and physical properties of organofluorine compounds, synthetic methods of these, their roles in pharmaceutical, agrochemical and material sciences. In particular, the book will emphasize on the usefulness of fluorination reaction, availability of fluorination agents, so that even graduate students who are unfamiliar to this field can understand and participate in this fascinating heteroatom chemistry.
Download or read book High Performance Pigments written by Hugh MacDonald Smith and published by John Wiley & Sons. This book was released on 2002 with total page 472 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume is the ideal companion to Wiley's trilogy: The Pigments Handbook (1988), Industrial Organic Pigments (1997), and Industrial Inorganic Pigments (1998). High Performance Pigments have become increasingly important in recent years, with a growth rate well in advance of the more classical types of pigments. The book offers both producers and users of High Performance Pigments the opportunity to review and update their understanding of latest technologies and market issues impacting both inorganic and organic High Performance Pigments, together with assessing key regulatory affairs, in this specialty niche of the chemical industry. The manufacture of High Performance Pigments is today a global industry. This is reflected in the multinational expertise of the over twenty experts, drawn from Europe, North America and Asia, who have authored chapters in this book. No professional today can afford to waste time on unfocussed research. This book will effectively help chemists, physicists, engineers, applications and regulatory specialists, and materials scientists to stay ahead in this fast-changing field.
Download or read book Flavin based Catalysis written by Radek Cibulka and published by Wiley-VCH. This book was released on 2021-09-07 with total page 300 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book gives a unique overview of this rapidly developing research field, presenting structures and properties of flavin derivatives as well as their proven application as bioinspired catalysts in various organocatalytic, biocatalytic, and photocatalytic reactions.
Download or read book Ring Enlargement in Organic Chemistry written by Manfred Hesse and published by . This book was released on 1991 with total page 256 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Herbicide Classes in Development written by Peter Böger and published by Springer. This book was released on 2011-09-23 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Chemical pest control is in use in practically every country in the world since agrochemicals play a decisive role in ensuring food supply and protection against damage by pests, insects and pathogenic fungi. Particularly in the half century since World War II, food production has risen dramatically in most parts of the world. In the last 20 years, the yield of major crops has roughly doubled in Western agriculture and there is still the potential for further achievements, particularly in the developing countries. The world's cereal and rice production, now more than 2 billion tons/year, has to increase by 2. 4% annually to cope with the rising food demand caused mainly by the growing population and improvement of living standards in most of the developing countries. Such a demand for food has to be achieved by higher yields from the restricted arable land already in use. Global farm land resources are about 1. 4 billion ha, of which 1. 2 billion ha is cultivated with major crops. Experts agree that a future substantial addition of new produc tive areas is unlikely. Those with a high yield potential are already in use; new fields with a lower output may possibly be obtained by cultivation of arid or cold areas. More recently, new areas of large-scale farmland have been devel oped in tropical regions of Latin America, primarily in Argentina and Brazil, at the cost of the destruction of tropical rain forest.
