Browsing by Author "Millan, Daniela"
Now showing 1 - 3 of 3
Results Per Page
Sort Options
Item Predicting the reaction mechanism of nucleophilic substitutions at carbonyl and thiocarbonyl centres of esters and thioesters(John Wiley & Sons, 2012) Ormazábal-Toledo, Rodrigo; Castro, Enrique; Santos, Jose; Millan, Daniela; Cañete, Alvaro; Contreras, Renato; Campodónico, PaolaIn nucleophilic substitution reactions at carbonyl centres, there are two possible channels. The first one occurs when the attack of nucleophilic agents takes place simultaneously with the departure of the nucleofuge. This process is named as concerted. The second possibility is the formation of a reaction intermediate, typically a tetrahedral intermediate from which the nucleofuge departs after passing through a second transition state. This second mechanism is defined as stepwise. Whether a concerted or stepwise mechanism is to be expected for a given reaction depends on several factors. Among these determinants are the nucleophilicity of the attacking group, the leaving group ability of the nucleofuge, and the solvent, which affects both the stability of the intermediate or the transition states involved. The role of the electrophilic centre can however become an important factor that can determine the reaction mechanism. In this work we show that the group nucleophilic Fukui function model may be used to rationalize and to predict the reaction mechanism of the title compounds towards alicyclic amines. In general, when the electrophilic carbon centre is attached to the soft sulfur atom, the reaction mechanism is predicted to follow a stepwise route. When the electrophilic carbon atom is attached to a harder oxygen centre, the reaction mechanism is determined by chemical substitution at the nucleofuge moiety. Experimental verification for a set of four substrates is presented.Item Reactions of Aryl Acetates with Secondary Alicyclic Amines in Ethanol/Water Mixtures: Effect of the Solvent Composition on the Kinetics and Mechanism(2011) Castro, Enrique A.; Millan, Daniela; Aguayo, Raúl; Campodónico, Paola; Santos, José G.We report a kinetic study on the reactions of secondary alicyclic amines toward 4-nitrophenyl, 2,4-dinitrophenyl, and 2,4,6-trinitrophenyl acetates (1, 2, and 3) in ethanol/water mixtures of different compositions. It is found that (i) the intermediate in the reaction of 1 is stabilized in a mixture of 90 vol% ethanol; (ii) for the reaction of 2, the mechanism is stepwise in water but concerted in the mixtures; (iii) For the reaction of 3, the mechanism is concerted along the whole range of composition; (iv) the effect of -NO(2) outweighs the solvent effect; (v) preferential solvation in the core of reaction can be ruled out. (C) 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: 687-693, 2011Item Self-Sustaining Supramolecular Ionic Liquid Gels for Dye Adsorption(2018) Rizzo, Carla; Marullo, Salvatore; Campodónico, Paola; Pibiri, Ivana; Dintcheva, Nadka; Noto, Renato; Millan, Daniela; D’Anna, FrancescaWater contamination is one of the main problems ofmodern society, and scientific research is continuously involved in identifying solutions able to preserve this valuable source. In this context, we characterized novel ionogels formed by organic salts with different anions. In particular, they show self-strengthening behavior, a quite unusual property for supramolecular gels, and they also exhibit a good load-bearing capacity. These ionogels are able to remove cationic dyes from wastewater. Thanks to their properties, they can be used in different apparatuses like dialysis membranes and as loading in adsorption columns. In the latter case over 95% removal is achieved in less than 10 min. Interestingly, soft materials can be reused for at least 20 cycles, partially regenerated, and reused for further 15 cycles. Comparison with data previously reported in the literature shows that this is a prerogative of this system and this represents not only an improvement but also a warranty oflow raw material production after wastewater treatment.