6 resultados para SUBSTITUTION-REACTIONS

em Archivo Digital para la Docencia y la Investigación - Repositorio Institucional de la Universidad del País Vasco


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[ES]La sustitución de los millones por el crecimiento en el precio de la sal que Felipe IV estableció en 1631 provocó reacciones generalizadas en toda Castilla, y en particular entre las provincias que se hallaban exentas de pagarlos. Son conocidos los violentos disturbios de Vizcaya. En cambio, poco se sabe acerca de lo sucedido en las otras dos Provincias Exentas. El presente artículo analiza, en conjunto, la actitud que tanto Vizcaya como Guipúzcoa y Álava adoptaron ante el nuevo impuesto. Aunque las tres coincidieron en rechazarlo, lo hicieron mediante discursos y métodos bien diferentes. No en vano, lejos de lo que suele pensarse no gozaban de una plena equiparación fiscal ni jurídica.

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Command and control regulation programs, particularly input constraints, typically fail to achieve stated objectives, because fishermen may substitute unregulated for regulated inputs. It is, thus, essential to have an understanding of the internal structure of production technology. A primal formulation is used to estimate a translog production function at the vessels level that includes fishing effort and fisherman’s skill. The flexibility of the selected functional permits the analysis of the substitution possibilities among inputs by estimating the elasticity of substitution with no prior constraints. Particular attention is paid to the empirical validation of fishing effort as an aggregate input, which implies either, the acceptation of the joint hypothesis that inputs making up effort are weakly separable from the inputs out of the subgroup or considering that effort is an intermediate input produced by a non-separable two stage technology. Cross sectional data from the Spanish purse seine fleet operating in the VIII Division European anchovy fishery provide evidence of limited input substitution possibilities among the inputs making up the empirically validated fishing effort translog micro-production function.

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In this review we summarize recent developments in inter- and intramolecular enantioselective carbolithiation reactions carried out in the presence of a chiral ligand for lithium, such as (-)-sparteine, to promote facial selection on a C=C bond. This is an attractive approach for the construction of new carbon-carbon bonds in an asymmetric fashion, with the possibility of introducing further functionalization on the molecule by trapping the reactive organolithium intermediates with electrophiles.

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A broad perspective of various factors influencing alkene selenenylation has been developed by concurrent detailed analysis of key experimental and theoretical data, such as asymmetric induction, stereochemistry, relative reactivities, and comparison with that of alkene sulfenylation. Alkyl group branching a to the double bond was shown to have the greatest effect on alkene reactivity and the stereochemical outcome of corresponding addition reactions. This is in sharp contrast with other additions to alkenes, which depend more on the degree of substitution on C=C or upon substituent electronic effects. Electronic and steric effects influencing asymmetric induction, stereochemistry, regiochemistry, and relative reactivities in the addition of PhSeOTf to alkenes are compared and contrasted with those of PhSCl.

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302 p. : gráf.