ABSTRACT
Fatty acid esters of 2-ethyl-1-hexanol (EH), 2-hexyl-1-decanol (HD), and isopropanol have been obtained from a mixture of ethyl esters obtained as a fish oil byproduct. Homogeneous base catalysis with alkaline hydroxides and alkoxides has been compared with the use of two commercially available immobilized lipases. The enzymatic methodology is more efficient in the case of the largest alcohol (HD) mainly because of the high stability of the immobilized enzymes upon recovery and reuse. In contrast, the use of a base as a catalyst is highly favorable in the case of isopropanol because of the rather poor activity of the lipases and the low price of the bases. With EH, the activity of lipases is good but the recoverability is not as efficient; hence, basic catalysts are again the most attractive alternative. The mixtures of esters obtained may be useful as hydraulic liquids given their viscosity values.
ABSTRACT
The mechanism of the copper(I)-catalyzed cyclopropanation reaction for methyl diazoacetate with both (Z)- and (E)-but-2-ene stereoisomers has been studied using the 6-311++G(d,p) basis set by means of M06-2X and O3LYP functionals. According to both methods, the rate-limiting step is the formation of a copper-carbene intermediate, formed by association between methyl diazoacetate and bis(acetonitrile)-copper(I) ion with the concomitant extrusion of dinitrogen. Cis/trans diastereoselectivity for the cyclopropanation reaction of a 1,2-disubstituted alkene ((Z)-but-2-ene) has been theoretically studied for the first time through the proper location of transition states on the potential-energy surface with the O3LYP method, since no transition structures could be found with the M06-2X functional due to the extreme flatness of the potential-energy surface. The calculated stereoselectivities involving two acetonitrile ligands or one dichloromethane molecule show qualitative agreement with experimental data. This study allows attributing the origin of the selectivity to steric interactions between the ligands of the catalyst system and the olefin substituents. The comparison between the corresponding activation barriers for the direct insertion step shows a higher reactivity for the Z stereoisomer of but-2-ene, consistently with the larger reactant destabilization through steric interactions.
ABSTRACT
Several kinds of polytopic chiral ligands (including ditopic, tritopic and tetratopic), based on the bis(oxazoline) and azabis(oxazoline) motifs, have been tested in the preparation of recoverable catalytic systems for the Henry reaction. The results obtained with the different ligands are, in general, good, but they point to the existence of a delicate balance between the coordinating ability of the ligand, the catalytic activity and the recovery of the catalyst by formation of the coordination polymer, related to the easiness to form oligomeric species in solution.
ABSTRACT
An efficient release-capture strategy for the recovery and reuse of enantioselective catalysts in the Henry reaction is described. This strategy is based on the precipitation of an insoluble coordination polymer at the end of each reaction, allowing easy separation from products. The coordination polymer is formed through aggregation of Cu(II) ions with ditopic bisoxazoline-based chiral ligands. Up to 11 catalytic cycles have been conducted keeping good yields and enantioselectivities.
Subject(s)
Aldehydes/chemistry , Nitro Compounds/chemical synthesis , Organometallic Compounds/chemistry , Oxazoles/chemistry , Polymers/chemistry , Catalysis , Copper/chemistry , Ligands , Molecular Structure , Nitro Compounds/chemistry , Organometallic Compounds/chemical synthesis , Polymers/chemical synthesis , StereoisomerismABSTRACT
A Hipertensão Arterial Sistêmica é uma doença crônica que envolve o aumento da pressão do sangue nas artérias. É uma doença multivariada, imperceptível nos estágios iniciais, na maioria das vezes progressiva e sempre perigosa, por isso, requer diagnóstico precoce e tratamento adequado. Os fatores etiológicos se encontram principalmente na existência de estilos de vida inadequados na comunidade em geral, e desde que sejam controlados, é possível reduzir o seu impacto. Por esta razão e com base na taxa atual de pacientes hipertensos na área de abrangência da UBS Urbano 2, município de Ouro Branco, Alagoas, esse TCC tem por objetivo elaborar um projeto de intervenção voltado para uma estratégia educacional, buscando diminuir hábitos e estilos de vida negativos na comunidade assistida. A partir da situação de morbidade e mortalidade prevalentes não somente na comunidade assistida, mas também no país e no estado, enfatiza-se o fortalecimento da promoção e prevenção na luta para evitar os fatores de risco e promover a saúde, enfatizando estilos de vida saudáveis desde a tenra idade de vida para neutralizar o aparecimento de hipertensão. Foram coletados dados por ocasião do diagnóstico situacional da Equipe de Saúde da Família que foram conseguidos a partir de bases secundárias tais como o Sistema de Informação da Atenção Básica (SIAB), base de dados de internet do Instituto Brasileiro de Geografia e Estatística e do Atlas de Desenvolvimento Humano municipal, além de entrevistas com informantes-chave e observação ativa. Esses dados foram utilizados, juntamente com revisão de literatura feita sobre o tema, na construção de uma proposta de intervenção, conforme proposta de Campos, Faria e Santos (2010), identificando e priorizando problemas, construindo propostas para o enfrentamento de tais situações.
