Search results for "SOLVENT"
showing 10 items of 1395 documents
A filter-press electrolytic cell with semi-continuous renewal of sacrifical electrodes
1989
Etude d'une cellule electrolytique dans laquelle une des electrodes est consummee avec remplacement de l'element sacrifie sans demontage de la cellule. Cette cellule est testee lors de l'electrocarboxylation de la N-phenylbenzalimine en acide amine
Do electrospray mass spectra of surfactants mirror their aggregation state in solution?
2011
One important feature in the gas phase chemistry of surfactants is to ascertain whether their aggregates produced by electrospray ionization reflect those formed in the starting solution. With this aim, we have performed ESI-MS, ESI-MS/MS and ER-MS spectra of bis(2-ethylhexyl)sulfosuccinate (AOTNa) solutions in different solvents, i.e. water, water/methanol, methanol and n-hexane. The results clearly indicate that, notwithstanding the strongly different aggregation state in solution (direct micelles in water and in water/methanol, molecular dispersion in methanol and reverse micelles in n-hexane) and marked effects of the solvent polarity on the total ionic current, the surfactant aggregate…
Free Energy, Enthalpy and Entropy from Implicit Solvent End-Point Simulations
2018
Free energy is the key quantity to describe the thermodynamics of biological systems. In this perspective we consider the calculation of free energy, enthalpy and entropy from end-point molecular dynamics simulations. Since the enthalpy may be calculated as the ensemble average over equilibrated simulation snapshots the difficulties related to free energy calculation are ultimately related to the calculation of the entropy of the system and in particular of the solvent entropy. In the last two decades implicit solvent models have been used to circumvent the problem and to take into account solvent entropy implicitly in the solvation terms. More recently outstanding advancement in both impli…
Stability of nitroaromatic specialty explosives in reversed-phase liquid chromatographic systems
2008
Abstract In this study, the stability of 2,4-dinitroanisole, 2,2′,4,4′,6,6′-hexanitrodiphenylsulfide, 2,3,4,6-tetranitroaniline, 2,4,6-trinitroaniline, 2,4,6-trinitroanisole, and 2,4,6-trinitrochlorobenzene in liquid chromatographic systems was studied under different solvent/eluent conditions. Stock solutions of the explosives were prepared in acetonitrile and diluted with acetone/water, acetonitrile/water, or methanol/water mixtures. Within 48 h, these working solutions were repeatedly injected onto a silica column and eluted with acetonitrile/water or methanol/water mobile phases. Under all conditions, 2,4-dinitroanisole was stable, whereas 2,4,6-trinitroaniline was stable only in the me…
Adsorption of a dye on clay and sand. Use of cyclodextrins as solubility-enhancement agents.
2007
Abstract Laboratory-scale studies were aimed at elucidating the physico-chemical aspects on the removal process of crystal violet (CV) from waters and solid substrates. The laponite clay (RD) and sand were chosen for the double aim at investigating them as CV adsorbents for water treatment and as substrates which mime the soil components. Sand is very effective in removing CV from waters. The cyclodextrins (CDs) were exploited as solubility-enhancement agents to remove CV from the solid substrates. They are powerful solvent media because they extract the CV from sand forming water-soluble CV/CD inclusion complexes and do not show affinity for sand. Optimum performance was shown by the modif…
Towards the design of organocatalysts for nerve agents remediation: The case of the active hydrolysis of DCNP (a Tabun mimic) catalyzed by simple ami…
2015
We report herein a study of the hydrolysis of Tabun mimic DCNP in the presence of different amines, aminoalcohols and glycols as potential suitable organocatalysts for DCNP degradation. Experiments were performed in CD3CN in the presence of 5% D2O, which is a suitable solvent mixture to follow the DCNP hydrolysis. These studies allowed the definition of different DCNP depletion paths, resulting in the formation of diethylphosphoric acid, tetraethylpyrophosphate and phosphoramide species as final products. Without organocatalysts, DCNP hydrolysis occurred mainly via an autocatalysis path. Addition of tertiary amines in sub-stoichiometric amounts largely enhanced DCNP depletion whereas non-te…
Barrier properties of anti-gas military garments, considering exposure to gas organic compounds
2020
The problems of determining the protective properties of barrier materials used for the production of body surface protection products of an isolative type are very actual. These garments are expected to have long-term resistance against permeation of toxic substances. The paper deals with the study of the effect of organic solvent vapours on the changes in protective properties of selected anti-gas protective garments commonly used by the North Atlantic Treaty Organization armed forces. Permeation measurements of selected gases with integral permeameter were performed to verify their barrier properties, surface changes after exposure to selected solvents by using a 3D optical profilometer,…
Experimental P-T-ro Measurements of Supercritical Mixtures of Carbon Dioxide, Carbon Monoxide, and Hydrogen and Semiquantitative Estimation of Their …
2007
The P-T-ρ behavior of the CO2-CO-H2 system was studied in the supercritical region under operative conditions close to those adopted to perform hydrogenation and hydroformylation reactions in dense CO 2, thus providing new interesting information on this fluid mixture. Experiments were performed in a fixed volume reactor in the temperature range from 298 K to 343 K changing the density and the composition of the fluid phase. The one-component (Hildebrand) solubility parameter of the mixture was estimated from experimentally measured P vs T profiles, and its dependence on the density and composition of the system was analyzed to study the antisolvent effect of the permanent gases. We have fo…
Microwave-assisted synthesis of PHEA-oligoamine copolymers as potential gene delivery systems
2009
Aims - Copolymers bearing oligoamines and having buffering capacity in the endosomal pH range seems very promising as non viral vectors in gene delivery, due to the great importance of endosomal escaping for an efficient endocellular DNA release. Aim of this paper was to prepare new copolymers based on α,β-poly-(N-2-hydroxyethyl)-D,L-aspartamide (PHEA) as polymeric backbone and bearing an oligoamine, such as diethylentriamine (DETA) in the side chain and useful for gene delivery. Moreover in order to reduce solvent volume and to make faster the reaction, microwave-assisted has been used. Materials and methods - PHEA copolymers bearing different amount of DETA were prepared by using bis(4-ni…
Proposal of Isobutyl Alcohol as Entrainer To Separate Mixtures Formed by Ethanol and Water and 1-Propanol and Water
2017
Isobutyl alcohol (IBA) has been proposed as a solvent to carry out the dehydration of ethanol and 1-propanol by means of a nonconventional distillation process. In this way, isobaric vapor–liquid equilibrium (VLE) and vapor–liquid–liquid equilibrium (VLLE) data at atmospheric pressure have been obtained for the ternary systems ethanol (1a) + water (2) + IBA (3) and 1-propanol (1b) + water (2) + IBA (3). Then, these data have been correlated to obtain a set of parameters capable of estimating VLE and VLLE. According to the results achieved, distillation sequences to separate water and ethanol or 1-propanol have been proposed. Finally, a study about the minimum amount of entrainer required to…