Cooperative effects of H+ and H- hydrido carbonyl ruthenium derivatives; role of homogeneous and heterogeneous protonic and lewis acids in catalytic hydrocarbonylation reactions

The role played by H+ hydrido iodocarbonyl and H- hydrido carbonyl ruthenium catalysts in the different catalytic steps of hydroformylation and hydroesterification of olefins, and in the homologation of alcohols has been investigated. The H- hydrido carbonyl species are mainly involved in the activation of olefins and in the hydrogenation of the acyl intermediates to aldehydes and alcohols, whereas the H+ hydrido iodocarbonyl derivatives are involved in the activation of alcohols and other oxygenated substrates, and in their carbonylation to esters. The cooperation between the two species, possible under particular reaction conditions, results in an improvement of the selectivity towards homologation (carbonylation plus hydrogenation) products. Heterogeneous Lewis acid promoters, easily recyclable from the reaction mixture, have also been successfully used in the hydrocarbonylation of alcohols, resulting in an increase of the carbonylation and homologation products. A reaction pathway in agreement with the experimental results is discussed. �� 1989.

Estudos sobre o uso de NbCl5 como ��cido de Lewis em rea����es de Povarov

Funda����o de Amparo �� Pesquisa do Estado de S��o Paulo (FAPESP)

Aplica����o de s��lica mesoporosa modificada com mol��culas contendo bases de Lewis na pr��-concentra����o de Cd(II) em amostras aquosas

Em raz��o ao uso intensivo e por ser altamente n��o-degrad��vel, o metal Cd (II) tem causado uma grande preocupa����o na sociedade moderna devido a sua capacidade de acumular-se em matrizes ambientais manifestando toxicidade. O projeto teve como objetivo o desenvolvimento da s��ntese da S��lica Mesoporosa para o ancoramento do ligante ��cido Rube��nico sobre a superf��cie do material. A caracteriza����o do mesmo, por espectroscopia na regi��o do infravermelho (FTIR), ap��s a etapa de funcionaliza����o indicou a presen��a de grupamento amina, com banda em 3350 cm-1, bandas na regi��o de 2940 e 2850 cm-1 atribu��das a grupos metileno e a atenua����o da banda C-Cl (700 cm-1), devido ao ancoramento da mol��cula do ligante. O material foi aplicado em experimentos de batelada e o efeito de tempo de contato e do pH sobre a adsor����o de ��ons Cd (II) foi avaliado. O material apresentou cin��tica r��pida, a qual foi alcan��ada em 1 minuto e a maior adsor����o foi atingida em pH 6 (pr��ximo ao ponto de carga zero) para ambos os metais. As condi����es ��timas obtidas foram aplicadas para a determina����o da capacidade m��xima de adsor����o. Os dados obtidos da isoterma de adsor����o foram aplicados �� Equa����o Linearizada de Langmuir, fornecendo 0,03 mmol g-1, com o coeficiente de determina����o dos dados sendo R�� de 0,9961. Na segunda etapa, o material modificado foi aplicado em sistema de fluxo cont��nuo, ajustando as melhores condi����es como massa de amostra, tipos de eluente bem como o volume de eluato. Os resultados das concentra����es do metal foram obtidos por determina����o direta por espectrometria de absor����o at��mica

Caracteriza����o biom��trica e supera����o de dorm��ncia em sementes de Chloroleucon foliolosum (Benth.) G. P. Lewis

The objectives of this work were performing the biometric characterization of seed Chloroleucon foliosolum (Benth) G. P. (Lewis) from the municipality Itua��u - BA, and analyze methods of scarification and temperature on germination. The seeds were characterized according to measurements of length, width and thickness, weight of thousand seeds, and water content. Were employed methods of scarification with sandpaper and sulfuric acid for 15 and 30 minutes, and not scarified seeds, combined with germination temperatures of 20, 25, 30 and 35 ��C. Percentage and germination speed index, and percentage of primary root protrusion, abnormal seedlings, hard seeds and dead seeds were evaluated. The means of length, width and thickness was 6.03, 4.30 and 3.47 mm, respectively. The weight of a thousand seeds was 67.3 g with water content of 6.1%. Whereas the percentage germination with normal seedling, the method of scarification with sulfuric acid for 15 or 30 minutes combined to germination temperatures of 25 or 30 ��C were effective in overcoming dormancy of Chloroleucon foliolosum.