Publicaciones 2011-2020

@article{RN273,
title = {Changes in the Snar Reaction Mechanism Brought About by Preferential Solvation},
author = { J. Alarcon-Esposito and R.A. Tapia and R. Contreras and P.R. Campodonico},
url = {/brokenurl#<Go to ISI>://WOS:000365328000069},
doi = {10.1039/c5ra20779g},
issn = {2046-2069},
year = {2015},
date = {2015-01-01},
journal = {Rsc Advances},
volume = {5},
number = {120},
pages = {99322-99328},
abstract = {We herein report an experimental and theoretical study on preferential solvation effects for the reactions of 1-fluoro and 1-chloro-2,4-dinitrobenzene towards morpholine in acetonitrile, water and mixtures of them of varying compositions. A detailed kinetic study opens the possibility of analyzing preferential solvation and reaction rates. The kinetic study was complemented with an exploration of the potential energy surface in order to analyze the nature of the molecular interactions. For the fluorine derivative, this analysis reveals that the solvation of the TS in the mode TS1F-water/MeCN clearly outweighs the solvation of TS1F-MeCN/water, thereby suggesting that there is preferential solvation in favor of the aqueous phase.},
keywords = {aminolysis, benzenesulfonates, binary ionic liquids, mixtures, molecules, nucleophilic-substitution pathways reactions, regioselectivity, secondary-amines, solvent},
pubstate = {published},
tppubtype = {article}
}

@article{RN225,
title = {Site Activation Effects Promoted by Intramolecular Hydrogen Bond Interactions in Snar Reactions},
author = { S. Gallardo-Fuentes and R.A. Tapia and R. Contreras and P.R. Campodonico},
url = {/brokenurl#<Go to ISI>://WOS:000340500300025},
doi = {10.1039/c4ra04725g},
issn = {2046-2069},
year = {2014},
date = {2014-01-01},
journal = {Rsc Advances},
volume = {4},
number = {58},
pages = {30638-30643},
abstract = {The nucleophilic aromatic substitution reaction of benzohydrazide derivatives towards 2-chloro-5nitropyrimidine is used as model system to experimentally and theoretically show that intramolecular hydrogen-bond formation operates as a perturbation that elicits a dual response at the reaction center of the transition state (TS) structure, by enhancing the electrophilicity of the pyrimidine moiety and the nucleophilicity of the nitrogen atom of the benzohydrazide fragment. The electronic mechanism can therefore be described as a (non-local) site activation problem.},
keywords = {aromatic electrophilicity, functionals, markovnikov model molecules, nucleophilic-substitution, potentials, reactivity, regioselectivity rule, secondary-amines, solvent},
pubstate = {published},
tppubtype = {article}
}

@article{RN163,
title = {Hydrogen Bond Contribution to Preferential Solvation in Snar Reactions},
author = { R. Ormazabal-Toledo and J.G. Santos and P. Rios and E.A. Castro and P.R. Campodonico and R. Contreras},
url = {/brokenurl#<Go to ISI>://WOS:000319649800012},
doi = {10.1021/jp4005295},
issn = {1520-6106},
year = {2013},
date = {2013-01-01},
journal = {Journal of Physical Chemistry B},
volume = {117},
number = {19},
pages = {5908-5915},
abstract = {Preferential solvation in aromatic nucleophilic substitution reactions is discussed using a kinetic study complemented with quantum chemical calculations. The model system is the reaction of a series of secondary alicyclic amines toward phenyl 2,4,6-trinitrophenyl ether in aqueous ethanol mixtures of different compositions. From solvent effect studies, it is found that only piperidine is sensitive to solvation effects, a result that may be traced to the polarity of the solvent composition in the ethanol/water mixture, which points to a specific electrophilic solvation in the aqueous phase.},
keywords = {amines aromatic behavior, binary chemical ether, kinetics, mixtures, molecules, nucleophilic-substitution, piperidine, probes, solvent},
pubstate = {published},
tppubtype = {article}
}

@article{sotodelgado2012catalytic,
title = {On the Catalytic Effect of Water in the Intramolecular Diels-Alder Reaction of Quinone Systems: A Theoretical Study},
author = { J. Soto-Delgado and A. Aizman and R. Contreras and L.R. Domingo},
url = {/brokenurl#<Go to ISI>://WOS:000311428400087},
doi = {10.3390/molecules171113687},
issn = {1420-3049},
year = {2012},
date = {2012-01-01},
journal = {Molecules},
volume = {17},
number = {11},
pages = {13687-13703},
abstract = {The mechanism of the intramolecular Diels-Alder (IMDA) reaction of benzoquinone 1, in the absence and in the presence of three water molecules, 1w, has been studied by means of density functional theory (DFT) methods, using the M05-2X and B3LYP functionals for exploration of the potential energy surface (PES). The energy and geometrical results obtained are complemented with a population analysis using the NBO method, and an analysis based on the global, local and group electrophilicity and nucleophilicity indices. Both implicit and explicit solvation emphasize the increase of the polarity of the reaction and the reduction of activation free energies associated with the transition states (TSs) of this IMDA process. These results are reinforced by the analysis of the reactivity indices derived from the conceptual DFT, which show that the increase of the electrophilicity of the quinone framework by the hydrogen-bond formation correctly explains the high polar character of this intramolecular process. Large polarization at the TSs promoted by hydrogen-bonds and implicit solvation by water together with a high electrophilicity-nucleophilicity difference consistently explains the catalytic effects of water molecules.},
keywords = {catalysis, characterization, chemistry density dft dft, diels-alder difference electrophilicity, functionals, index, indices, intramolecular local molecules, polar quantitative reactions, reactivity regioselectivity, solvent, thermochemistry, water},
pubstate = {published},
tppubtype = {article}
}

@article{RN1_98,
title = {Adsorption Behavior of Hydrophobically Modified Polyelectrolytes onto Amino- or Methyl-Terminated Surfaces},
author = { X. Briones and M.V. Encinas and D.F.S. Petri and J. Pavez and R.A. Tapia and M. Yazdani-Pedram and M. Urz\'{u}a},
url = {/brokenurl#<Go to ISI>://WOS:000296598300017},
doi = {10.1021/la2025632},
issn = {0743-7463},
year = {2011},
date = {2011-01-01},
journal = {Langmuir},
volume = {27},
number = {22},
pages = {13524-13532},
abstract = {The adsorption of hydrophobically modified polyelectrolytes derived from poly(maleic anhydride-alt-styrene) (P(MA-alt-St)) containing in their side chain aryl-alkyl groups onto amino- or methyl-terminated silicon wafers was investigated. The effect of the spacer group, the chemical nature of the side chain, molecular weight of polyelectrolyte, and ionic strength of solution on the polyelectrolyte adsorbed amount was studied by null ellipsometry. The adsorbed amount of polyelectrolyte increased with increasing ionic strength, in agreement with the screening-enhanced adsorption regime, indicating that hydrophobic interactions with the surface play an important role in the adsorption process. At constant ionic strength, the adsorbed amount was slightly higher for polyelectrolytes with larger alkyl side chain and decreased with the hydrophobicity of aryl group. The adsorption behavior is discussed in terms of the side chain flexibility of the polymer. Characteristics of the adsorbed layer were studied by atomic force microscopy (AFM) and contact angle measurements. AFM images show the presence of aggregates and closed globular structure of polyelectrolyte onto the amino- or methyl-terminated surface, which agrees with a 3D and 2D growth mechanism, respectively. Fluorescence measurements showed that the aggregation of polyelectrolyte containing the hydrophobic naphthyl group occurs already in the solution. However, the aggregation of polyelectrolytes containing the phenyl group in its side chain is not observed in solution but is induced by the amino-terminated surface. This difference can be explained in terms of the higher flexibility of side chain bearing the phenyl group. The polyelectrolyte films showed a high chemical heterogeneity and moderate hydrophobicity.},
keywords = {anhydride), carboxymethyl cellulose, charge complexes, layers, silica, solid-surfaces, solvent, sulfate},
pubstate = {published},
tppubtype = {article}
}