Libros de Química, página 3 de 133

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Todos los materiales poliméricos, sintéticos o naturales sufren reacciones de oxidación térmica que afectan su vida útil. Los efectos de dicha descomposición varían de un polímero a otro. Las diferencias se deben a la cristalinidad, la estructura y los residuos del catalizador que contenga cada uno. La presente obra analiza los principales tipos de antioxidantes y sus caracteristicas. La importancia del texto reside en que presenta un estudio bien documentado acerca de los estabilizadores UV que constituyen la forma de prevenir, o al menos reducir, el daño causado por agentes capaces de actuar durante los procesos fisicos y quimicos de la degradacion.

For more than a quarter century, Cotton and Wilkinson''s Advanced Inorganic Chemistry has been the source that students and professional chemists have turned to for the background needed to understand current research literature in inorganic chemistry and aspects of organometallic chemistry. Like its predecessors, this updated Sixth Edition is organized around the periodic table of elements and provides a systematic treatment of the chemistry of all chemical elements and their compounds. It incorporates important recent developments with an emphasis on advances in the interpretation of structure, bonding, and reactivity. From the reviews of the Fifth Edition: * "The first place to go when seeking general information about the chemistry of a particular element, especially when up-to-date, authoritative information is desired." -Journal of the American Chemical Society. * "Every student with a serious interest in inorganic chemistry should have [this book]." -Journal of Chemical Education. * "A mine of information . . . an invaluable guide." -Nature. * "The standard by which all other inorganic chemistry books are judged."-Nouveau Journal de Chimie. * "A masterly overview of the chemistry of the elements."-The Times of London Higher Education Supplement. * "A bonanza of information on important results and developments which could otherwise easily be overlooked in the general deluge of publications." -Angewandte Chemie.

Since its original appearance in 1977, Advanced Organic Chemistry has maintained its place as the premier textbook in the field, offering broad coverage of the structure, reactivity and synthesis of organic compounds. As in the earlier editions, the text contains extensive references to both the primary and review literature and provides examples of data and reactions that illustrate and document the generalizations. While the text assumes completion of an introductory course in organic chemistry, it reviews the fundamental concepts for each topic that is discussed. The two-part fifth edition has been substantially revised and reorganized for greater clarity. Among the changes include: updated material reflecting advances in the field since 2001''s Fourth Edition, especially in computational chemistry; a companion Web site that provides digital models for study of structure, reaction and selectivity; and, solutions to the exercises provided to instructors online. The control of reactivity to achieve specific syntheses is one of the overarching goals of organic chemistry. Part B describes the most general and useful synthetic reactions, organized on the basis of reaction type.Together with "Part A: Structure and Mechanisms", the two volumes are intended to provide the advanced undergraduate or beginning graduate student in chemistry with a sufficient foundation to comprehend and use the research literature in organic chemistry.

Since its original appearance in 1977, Advanced Organic Chemistry has maintained its place as the premier textbook in the field, offering broad coverage of the structure, reactivity and synthesis of organic compounds. As in the earlier editions, the text contains extensive references to both the primary and review literature and provides examples of data and reactions that illustrate and document the generalizations. While the text assumes completion of an introductory course in organic chemistry, it reviews the fundamental concepts for each topic that is discussed. The two-part fifth edition has been substantially revised and reorganized for greater clarity. Among the changes includes updated material that reflects advances in the field since 2001''s Fourth Edition, especially in computational chemistry; a companion Web site that provides digital models for study of structure, reaction and selectivity; and, solutions to the exercises provided to instructors online.The material in Part A is organized on the basis of fundamental structural topics such as structure, stereochemistry, conformation and aromaticity and basic mechanistic types, including nucleophilic substitution, addition reactions, carbonyl chemistry, aromatic substitution and free radical reactions. Together with Part B: Reaction and Synthesis, the two volumes are intended to provide the advanced undergraduate or beginning graduate student in chemistry with a sufficient foundation to comprehend and use the research literature in organic chemistry.

¿Cómo habrá hecho quien comercializa un fármaco o un suplemento alimenticio para tener la certeza de que este no irá a causar algún efecto negativo sobre la salud? Por el solo hecho de que algo sea natural, ¿queda automaticamente exento de cualquier efecto toxico? ¿Donde esta la proteccion al consumidor, sano o enfermo, que es quien, en ultima instancia, pagara las consecuencias? Frente a dudas como estas, este libro intenta indagar sobre las garantias de aquellos compuestos que se consumen para mantener o mejorar la salud. Por un lado, describe los fundamentos detras del desarrollo de agentes terapeuticos descubiertos mediante la metodologia cientifica, y la complejidad que rodea su sintesis, analisis y controles efectivos para su puesta en circulacion en el mercado. Por el otro, cuestiona la legitimidad de las afirmaciones acerca de los beneficios de los productos naturales o ecologicos, denominados nutraceuticos, que se nos ofrecen como suplementos de alimentacion y la salud. El autor vuelca en esta obra su preocupacion personal por la percepcion popular hacia la naturaleza de los productos curativos que se hallan a nuestro alcance y eleccion. Su particular experiencia, incluyendo la profesional, le permite conjugar y analizar objetivamente que hay de ciencia y cuanto de ?chachara? en el negocio de la salud. El libro tambien marca las diferencias metodologicas que existen entre la medicina convencional y la alternativa, asi como las razones por las cuales ambas seguiran coexistiendo.