Elsevier bv sep 2004 (3 risultati)

Taschenbuch. Condizione: Neu. Neuware - The world is chiral. Most of the molecules in it are chiral, and asymmetric synthesis is an important means by which enantiopure chiral molecules may be obtained for study and sale. Using examples from the literature of asymmetric synthesis (more than 1300 references), the aim of this book is to present a detailed analysis of the factors that govern stereoselectivity in organic reactions. It is important to note that the references were each individually checked by the authors to verify relevance to the topics under discussion. The study of stereoselectivity has evolved from issues of diastereoselectivity, through auxiliary-based methods for the synthesis of enantiomerically pure compounds (diastereoselectivity followed by separation and auxiliary cleavage), to asymmetric catalysis. In the latter instance, enantiomers (not diastereomers) are the products, and highly selective reactions and modern purification techniques allow preparation - in a single step - of chiral substances in 99% ee for many reaction types. After an explanation of the basic physical-organic principles of stereoselectivity, the authors provide a detailed, annotated glossary of stereochemical terms. A chapter on Analytical Methods provides a critical overview of the most common methods for analysis of stereoisomers. The authors then follow the 'tried-and-true' format of grouping the material by reaction type. Thus, there are four chapters on carbon-carbon bond forming reactions (enolate alkylations, organometal additions to carbonyls, aldol and Michael reactions, and cycloadditions and rearrangements), one chapter on reductions and hydroborations (carbon-hydrogen bond forming reactions), and one on oxidations (carbon-oxygen and carbon-nitrogen bond forming reactions). Leading references are provided to natural product synthesis that have been accomplished using a given reaction as a key step. In addition to tables of examples that show high selectivity, a transition state analysis is presented to explain - to the current level of understanding - the stereoselectivity of each reaction. In one case (Cram's rule) the evolution of the current theory is detailed from its first tentative (1952) postulate to the current Felkin-Anh-Heathcock formalism. For other reactions, only the currently accepted rationale is presented. Examination of these rationales also exposes the weaknesses of current theories, in that they cannot always explain the experimental observations. These shortcomings provide a challenge for future mechanistic investigations.…

Buch. Condizione: Neu. Neuware - This book on wetlands ecosystems in Asia deals with function and management. It is the first volume in the Developments in Ecosystems series.

Buch. Condizione: Neu. Neuware - The history of channel catfish farming in the United States serves as a model for the development of pond-based aquaculture industries worldwide. Channel catfish farming is the largest and economically most important aquaculture industry in the United States. In 2003, over 300,000 metric tons (662 million pounds) of channel catfish were processed, representing about half the total United States aquaculture production. Demand for farm-raised catfish is strong, with record processing years in 2002 and 2003. In 22 chapters written by active scientists in the field, Biology and Culture of Channel Catfish comprehensively synthesizes over 30 years of research on this American icon. Throughout the book, fundamental biological aspects of channel catfish are linked to practical culture techniques.Topics include:¿ Latest information on reproductive physiology, genetics, and breeding¿ Comprehensive treatment of catfish nutrition, feeds, and feeding practices¿ Water quality management and pond dynamics¿ In-depth review of immunology in channel catfish¿ Practical information on diseases and health management¿ Techniques for commercial culture, including innovative techniques such as raceways, recirculating systems, and partitioned aquaculture systems¿ Catfish economics and marketing¿ Exploration of environmental concerns, including recommended Best Management Practices.…