Silica gel

About: Silica gel is a research topic. Over the lifetime, 22313 publications have been published within this topic receiving 325516 citations. The topic is also known as: Amorphous silica & Precipitated amorphous silica.

Fluorous synthesis with fewer fluorines (light fluorous synthesis): Separation of tagged from untagged products by solid-phase extraction with fluorous reverse-phase silica gel

Abstract: Fluorous synthesis involves tagging an organic substrate with a fluorinated tag for the purposes of separation. To date, techniques of fluorous synthesis have relied on liquid−liquid extractions. This paper applies a simple solid−liquid extraction procedure over fluorous reverse-phase silica gel (silica with a fluorocarbon bonded phase) for use in fluorous synthesis. Four amino acids were tagged on nitrogen with the C9F19CO− group, and the resulting acids were coupled in a parallel experiment with an excess of four amines. The resulting 16 crude fluorous amide products were separated from all the coupling reagents and excess amine by two-stage filtration through fluorous silica. In 15 of the 16 cases, the products were isolated in good to excellent yield and purity. All of the products are soluble in organic solvents and none is expected to have any significant solubility in fluorous solvents, so the experiment dramatically illustrates the advantages of the solid−liquid extraction over the liquid−liquid e...

The role of nitroaromatic compounds in the direct-acting mutagenicity of diesel particle extracts.

Abstract: The Salmonella mutation assay has been adapted to a number of experimental procedures used to characterize the chemical components and molecular mechanisms involved in the direct-acting mutagenicity of diesel particle extracts. The mutagens were found to be unreactive towards purified DNA. Mutagenic activity was decreased in nitroreductase-deficient bacteria and increased in the absence of oxygen, suggesting that bacterial enzymes active the mutagens. The extract was fractionated by thin layer chromatography using both normal and reverse phase silica gel plates. On normal silica plates, a separation was made between unsubstituted PAH, nitro-PAH and the more polar aromatic compounds. About a third of the mutagenic activity in the particle extract was recovered in fractions containing monosubstituted nitro-PAH compounds. The absorption spectra and reverse phase chromatographic properties indicate 1-nitropyrene is a predominant component but not the only mutagen in these fractions. The remaining activity was in the more polar fractions, and mutagenicity assays using anaerobic conditions and nitro-reductase-deficient bacteria suggest they contain other nitro-substituted compounds.