Topic
Zwitterion
About: Zwitterion is a research topic. Over the lifetime, 2230 publications have been published within this topic receiving 44972 citations. The topic is also known as: inner salt & zwitterionic.
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TL;DR: The new ionic liquids combine the low volatility and ease of separation from product normally associated with solid acid catalysts, with the higher activity and yields normally found using conventional liquid acids.
Abstract: The reaction of triphenylphosphine or N-butylimidazole with cyclic sultones gives zwitterions that are subsequently converted into ionic liquids by reaction with trifluoromethane sulfonic acid or p-toluenesulfonic acid. The resulting ionic liquids have cations to which are tethered alkane sulfonic acid groups. These Bronsted acidic ionic liquids are useful solvent/catalysts for several organic reactions, including Fischer esterification, alcohol dehydrodimerization and the pinacol rearrangement. The new ionic liquids combine the low volatility and ease of separation from product normally associated with solid acid catalysts, with the higher activity and yields normally found using conventional liquid acids.
1,120 citations
TL;DR: In this article, the rates of homogeneous reaction of mono-, di- and tri-ethanolamine by various workers are compared and it seems probable that a zwitterion is the intermediate in the formation of carbamate and that the reaction of DEA (but not of MEA) is catalysed by bases
925 citations
TL;DR: In this paper, the authors provide an overview on the kinetics of the reaction of CO2 with aqueous solutions of alkanolamines, and various reaction mechanisms that are used to interpret experimental kinetic data.
Abstract: Alkanolamines are the most popular absorbents used to remove CO2 from process gas streams. Therefore, the CO2 reaction with alkanolamines is of considerable importance. The aim of this article is to provide an overview on the kinetics of the reaction of CO2 with aqueous solutions of alkanolamines. The various reaction mechanisms that are used to interpret experimental kinetic data – zwitterion, termolecular and base-catalyzed hydration – are discussed in detail. Recently published data on reaction kinetics of individual amine systems and their mixtures are considered. In addition, the kinetic behavior of several novel aminebased solvents that have been proposed in the literature is analyzed. Generally, the reaction of CO2 with primary, secondary and sterically hindered amines is governed by the zwitterion mechanism, whereas the reaction with tertiary amines is described by the base-catalyzed hydration of CO2.
613 citations
TL;DR: A thorough ab initio study of how the addition of successive water molecules shifts the gas phase zwitterion-neutral equilibrium of the amino acid glycine toward that of the solution phase is presented in this paper.
Abstract: A thorough ab initio study of how the addition of successive water molecules shifts the gas phase zwitterion-neutral equilibrium of the amino acid glycine toward that of the solution phase is presented. Of particular interest is the number of water molecules necessary to stabilize the zwitterion, and how the solvent effects conformational preference. It is found that two water molecules can stabilize the glycine zwitterion, that is, give rise to a potential energy minimum with at least one vibrational level. The results are analyzed and explained using localized charge distributions. 35 refs., 11 figs., 4 tabs.
399 citations
TL;DR: It is shown from both simulations and experiments that zwitterion functionalized carbon nanotubes (CNTs) can be used to construct highly efficient desalination membranes and theoretical predictions indicate that an ideal CNT/polymer membrane having a loading of 20 wt % CNTs would have a maximum flux of about 20000 GFD at the conditions of the authors' experiments.
Abstract: We have shown from both simulations and experiments that zwitterion functionalized carbon nanotubes (CNTs) can be used to construct highly efficient desalination membranes. Our simulations predicted that zwitterion functional groups at the ends of CNTs allow a high flux of water, while rejecting essentially all ions. We have synthesized zwitterion functionalized CNT/polyamide nanocomposite membranes with varying loadings of CNTs and assessed these membranes for water desalination. The CNTs within the polyamide layer were partially aligned through a high-vacuum filtration step during membrane synthesis. Addition of zwitterion functionalized CNTs into a polyamide membrane increased both the flux of water and the salt rejection ratio. The flux of water was found to increase by more than a factor of 4, from 6.8 to 28.7 GFD (gallons per square foot per day), as the fraction of CNTs was increased from 0 to 20 wt %. Importantly, the ion rejection ratio increased slightly from 97.6% to 98.6%. Thus, the nanotubes ...
336 citations