Search results for "Green chemistry"
showing 10 items of 159 documents
ChemInform Abstract: Recyclable Heterogeneous Palladium Catalysts in Pure Water: Sustainable Developments in Suzuki, Heck, Sonogashira and Tsuji-Tros…
2010
This review summarizes the progress made essentially these last ten years on heterogeneous palladium catalysis in pure water. The work covers four important palladium-catalyzed transformations for carbon-carbon bond formation: Suzuki, Heck, Sonogashira and Tsuji-Trost reactions. The discussion focuses on the efficiency and reusability of the heterogeneous catalysts as well as on the experimental conditions from a sustainable chemistry point of view. The review is introduced by a discussion on mechanistic aspects inherent to heterogeneous catalysis.
Renaissance of Electrosynthetic Methods for the Construction of Complex Molecules
2014
Current affairs: Efficient N,N dimerization by using an electric current is a recent powerful example of preparative electrosynthesis where conventional reagents fail. The general and practical nature of this method as well as other applications will breathe new life into the electroorganic synthesis of complex molecules.
Waste-free electrochemical oxidation of alchools in water
2006
We describe a new sol-gel molecular electrode made of a thin layer of organosilica doped with the nitroxyl radical TEMPO (2,2,6,6-tetrame-thylpiperidine-1-oxyl) electrodeposited on the surface of an ITO-coated glass and its employment as a selective and versatile oxidation catalyst in the electrochemical conversion of different alcohols to carbonyl compounds. Environmentally friendly water or a water/acetonitrile mixture buffered with bicarbonate is used as solvent. The electrode is highly stable and it can be reused for a prolonged period of time allowing easy separation from the products.
An environmentally friendly (“green”) reversed-phase liquid chromatography method for UV filters determination in cosmetics
2005
Abstract A green procedure based on reversed-phase liquid chromatography with gradient elution using environmentally friendly solvents, has been developed to determine 18 UV filters, which are most used in Europe nowadays as sunscreen in cosmetics. Samples were weighed and dissolved in ethanol. Two aliquots were taken from the initial sample solution to prepare two solutions, so analytes could be determined chromatographically in two groups (the most fat-soluble and the easily water-soluble ones) using a different gradient elution program for each group. The mobile phases were based on mixtures of ethanol and 1% acetic acid or 1% sodium acetate buffer pH 4.75. The same C18 stationary phase …
The Use of Amberlite Adsorbents for Green Chromatography Determination of Volatile Organic Compounds in Air
2012
Passive samplers have been widely used for volatile organic compounds determination. Following the green chemistry tendency of the direct determination of adsorbed compounds in membrane-based devices through using head space direct chromatography analysis, this work has evaluated the use of Amberlite XAD-2, XAD-4, and XAD-16 adsorbents as a filling material for passive samplers. Direct analysis of the membranes by HS-GC-MS involves a solvent-free method avoiding any sample treatment. For exposed membranes, recoveries ranged from 10% to 203%, depending on the compound and adsorbent used. The limit of the detection values ranged from 1 to 140 ng per sampler. Acceptable precision and sensitivi…
Biotransformations of monoterpenes by photoautotrophic micro-organisms.
2014
Summary Monoterpenes are widely used in food technology, cosmetic and pharmaceutical industries and as compounds of agricultural importance. It is known that compounds comprising this class can be transformed by a variety of organisms, namely by: bacteria, fungi, yeasts, plants or isolated enzymes. Biotransformations, as one of the most important tools of green chemistry, allow obtaining new products using whole cells of micro-organisms or isolated enzymes in mild reaction conditions. Therefore, biotransformations of monoterpenes, by different type of reaction such as: epoxidation, oxidation and stereoselective hydroxylation, resulted in the production of so desired, enantiomerically define…
Determination of Mercury in Milk by Cold Vapor Atomic Fluorescence: A Green Analytical Chemistry Laboratory Experiment
2011
Green analytical chemistry principles were introduced to undergraduate students in a laboratory experiment focused on determining the mercury concentration in cow and goat milk. In addition to traditional goals, such as accuracy, precision, sensitivity, and limits of detection in method selection and development, attention was paid to the evaluation of green parameters of the analytical methods. Milk samples were evaluated by cold vapor atomic fluorescence spectrometry (CV-AFS) and the wastes were minimized by co-precipitation with Fe(III).
The Concept of Green Analytical Chemistry
2012
Three years ago, when we published our review paper on Green Analytical Chemistry [1] it was clear that, at this time, Green Chemistry was a well established paradigm well supported by more than 50 published books, an increasing number of research teams who influenced the scientific literature and involved the editions of special journals like
Strain Release Chemistry of Photogenerated Small‐Ring Intermediates
2021
Abstract Photochemical processes, such as isomerizations and cycloadditions, have proven to be very useful in the construction of highly strained molecular frameworks. Photoinduced ring strain enables subsequent exergonic reactions which do not require the input of additional chemical energy and provides a variety of attractive synthetic options leading to complex structures. This review covers the progress achieved in the application of sequences combining excitation by ultraviolet light to form strained intermediates, which are further transformed to lower energy products in strain‐release reactions. As ring strain is considerable in small ring systems, photogenerated three‐ and four‐memb…