Uma acetilação eficiente e econômica do 1,2:3,4-di-O-isopropilideno-α-D-galactopiranose utilizando anidrido acético ativado in situ pela argila montmorilonita K10

Abstract

Resumo A síntese do 6-acetil 1,2:3,4-di-O-isopropilideno-α-D-galactopiranose a partir da reação de acetilação do 1,2:3,4-di-O-isopropilideno-α-D-galactopiranose utilizando a argila montmorilonita K10 como promotor é descrita. O protocolo é rápido, eficiente, econômico, livre de solvente e quimiosseletivo. O produto foi obtido em excelente rendimento (95%), curto tempo reacional (7,5 min), em temperatura ambiente e sem a necessidade de purificação adicional. Adicionalmente, essa argila manteve sua atividade catalítica por três ciclos reacionais sem diminuição de eficiência.

Influence of the additivation process on cation exchange capacity and viscosity of bentonitic clay dispersions

“…Bentonite clays have received a prominent attention from researchers of different areas of knowledge, since these materials have numerous applications in the most varied industrial sectors [1][2][3][4], and can be defined in a simplistic way as a material consisting essentially of montmorillonite, which has a particle size of less than 2.0 μm [1,[5][6][7]. In addition, they have the chemical composition and formula of the 'theoretical' or extreme montmorillonite unit cell of the (Al 3.33 Mg 0.67 )Si 8 O 20 (OH) 4 M + 0.67 series, where M + is a monovalent cation.…”

“…The exchangeable cation content, expressed in milliequivalents (meq) of the cation per 100 g of clay, is called cation exchange capacity (CEC). The stacking of the structural layers is governed by relatively weak polar and van der Waals forces and, between these layers, there are gaps called galleries or intermediary layers in which the exchangeable cations, such as Na + , Ca 2+ , and Li + , are fixed electrostatically [1,8]. The physicochemical properties of clay minerals are closely associated with surface and surface charge phenomena.…”

“…The varieties commercialized today are predominantly polycationic, containing other clay minerals, such as illite and kaolinite, as well as considerable amounts of non-clay components such as quartz and feldspar, which in turn compromise their technological applications [3,[9][10][11][12]. The polycationic bentonite clays can be changed to sodic form by a reversible double-exchange chemical reaction using sodium carbonate (Na 2 CO 3 ), since the interlamellar distance in the bentonites is higher when the lamellae have their charge compensated by the sodium ion, of lower valence, allowing the penetration of a greater amount of water in the space between the lamellae [1,16,17]. This explains why the expansion capacity of sodium bentonite is much higher than that of the calcium type [20].…”

Síntese e avaliação antifúngica do benzil 2,3-didesoxi-α-D-eritro-hex-2-enopiranosídeo contra espécies de Candida spp. e estudo da associação com anfotericina B

“…Os solventes comerciais foram purificados de acordo com os protocolos descritos na literatura. 24 O hexano e o acetato de etila foram destilados com coluna de vigreaux 25…”