Elvira Santos

Cotton effect of dimedone condensation compounds with optically active amines

Abstract The Cotton effect of dimedone condensation products of several optically active aliphatic, alicyclic, and aromatic amines was examined by rotatory dispersion and circular dichroism techniques. A correlation has been established between the sign of the Cotton effect and the absolute configuration of the asymmetric center under investigation. All dimedonyl derivatives of aliphatic and alycyclic amines investigated in this study having the ( R ) configuration exhibit a positive Cotton effect in the 280 mμ region. A negative Cotton effect is observed for compounds showing the ( S ) configuration. The hydrochlorides of some dimedonyl derivatives were prepared. The sign of the Cotton effect is the same as in the free base. Solvent-dependent equilibria were noted.

Synthesis of pyridine oxides and isoxazolines from 4-(2-oxoalkylidene)-pyrans

The reaction of 2,6-disubstituted and 2,5,6-trisubstituted 4-(2-oxoalkylidene)pyrans with hydroxylamine yields oximes of 4-(2-oxoalkyl)pyridine N-oxides or substituted Δ2-isoxazolines, or a mixture thereof. The factors influencing the competition between the formation of these two types of product are discussed.

Enseñanza Experimental y Química Combinatoria: Obtención de Esteres y Amidas, utilizando dos Fuentes de Energía Térmica y Microondas

Resumen Se han disenado una serie de experimentos de laboratorio con el fin de permitir a los alumnos resolver problemas para que a traves del trabajo experimental individual y el trabajo en equipo utilizando las bases de la quimica combinatoria. Se ha usado la sintesis de esteres del acido p -aminobenzoico con alcoholes primarios con un numero de atomos de carbono creciente y alcoholes ramificados para ver como se modifica la reactividad. Ademas se exploro el efecto que tiene el utilizar dos fuentes de energia: el calentamiento por conduccion y el uso de microondas. Por otro lado, se realizo la sintesis de acetanilidas con p -aminofenol o anilina con el fin de comparar la reactividad de las aminas aromaticas. Los estudiantes desarrollaron aptitudes criticas del laboratorio de quimica organica y aumentaron sus habilidades del trabajo en equipo. Palabras clave: Quimica combinatoria, esterificacion, microondas, amidas, analisis estructura-reactividad. Experimental and Combinatorial Chemistry Education: Preparation of Esters and Amides, using two Sources of Energy Thermal and Microwave