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Batista PR, Penna TC, Ducati LC, Correra TC. p-Aminobenzoic acid protonation dynamics in an evaporating droplet by ab initio molecular dynamics. Phys Chem Chem Phys 2021; 23:19659-19672. [PMID: 34524295 DOI: 10.1039/d1cp01495a] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Protonation equilibria are known to vary from the bulk to microdroplet conditions, which could induce many chemical and physical phenomena. Protonated p-aminobenzoic acid (PABA + H+) can be considered a model for probing the protonation dynamics in an evaporating droplet, as its protonation equilibrium is highly dependent on the formation conditions from solution via atmospheric pressure ionization sources. Experiments using diverse experimental techniques have shown that protic solvents allow formation of the O-protomer (PABA protonated in the carboxylic acid group) stable in the gas phase, while aprotic solvents yield the N-protomer (protonated in the amino group) that is the most stable protomer in solution. In this work, we explore the protonation equilibrium of PABA solvated by different numbers of water molecules (n = 0 to 32) using ab initio molecular dynamics. For n = 8-32, the protonation is either at the NH2 group or in the solvent network. The solvent network interacts with the carboxylic acid group, but there is no complete proton transfer to form the O-protomer. For smaller clusters, however, solvent-mediated proton transfers to the carboxylic acid were observed, both via the Grotthuss mechanism and the vehicle or shuttle mechanism (for n = 1 and 2). Thermodynamic considerations allowed a description of the origins of the kinetic trapping effect, which explains the observation of the solution structure in the gas phase. This effect likely occurs in the final evaporation steps, which are outside the droplet size range covered by previous classical molecular dynamics simulations of charged droplets. These results may be considered relevant in determining the nature of the species observed in the ubiquitous ESI based mass spectrometry analysis, and in general for droplet chemistry, explaining how protonation equilibria are drastically changed from bulk to microdroplet conditions.
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Affiliation(s)
- Patrick R Batista
- Department of Fundamental Chemistry, Institute of Chemistry - University of São Paulo, Av. Prof. Lineu Prestes, 748, Cidade Universitária, São Paulo, SP, Brazil.
| | - Tatiana C Penna
- Department of Fundamental Chemistry, Institute of Chemistry - University of São Paulo, Av. Prof. Lineu Prestes, 748, Cidade Universitária, São Paulo, SP, Brazil.
| | - Lucas C Ducati
- Department of Fundamental Chemistry, Institute of Chemistry - University of São Paulo, Av. Prof. Lineu Prestes, 748, Cidade Universitária, São Paulo, SP, Brazil.
| | - Thiago C Correra
- Department of Fundamental Chemistry, Institute of Chemistry - University of São Paulo, Av. Prof. Lineu Prestes, 748, Cidade Universitária, São Paulo, SP, Brazil.
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Wild M, Stolz F, Naumov S, Abel B. On the in situ formation of carbenes in ionic liquids. Mol Phys 2021. [DOI: 10.1080/00268976.2021.1974589] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Affiliation(s)
- Martin Wild
- Leibniz Institute of Surface Engineering (IOM), Leipzig, Germany
- Wilhelm-Ostwald-Institute for Physical and Theoretical Chemistry, University Leipzig, Leipzig, Germany
| | - Ferdinand Stolz
- Leibniz Institute of Surface Engineering (IOM), Leipzig, Germany
- Wilhelm-Ostwald-Institute for Physical and Theoretical Chemistry, University Leipzig, Leipzig, Germany
| | - Sergej Naumov
- Leibniz Institute of Surface Engineering (IOM), Leipzig, Germany
| | - Bernd Abel
- Leibniz Institute of Surface Engineering (IOM), Leipzig, Germany
- Wilhelm-Ostwald-Institute for Physical and Theoretical Chemistry, University Leipzig, Leipzig, Germany
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Urban RD, Fischer TG, Charvat A, Wink K, Krafft B, Ohla S, Zeitler K, Abel B, Belder D. On-chip mass spectrometric analysis in non-polar solvents by liquid beam infrared matrix-assisted laser dispersion/ionization. Anal Bioanal Chem 2021; 413:1561-1570. [PMID: 33479818 PMCID: PMC7921053 DOI: 10.1007/s00216-020-03115-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2020] [Revised: 12/01/2020] [Accepted: 12/07/2020] [Indexed: 12/15/2022]
Abstract
By the on-chip integration of a droplet generator in front of an emitter tip, droplets of non-polar solvents are generated in a free jet of an aqueous matrix. When an IR laser irradiates this free liquid jet consisting of water as the continuous phase and the non-polar solvent as the dispersed droplet phase, the solutes in the droplets are ionized. This ionization at atmospheric pressure enables the mass spectrometric analysis of non-polar compounds with the aid of a surrounding aqueous matrix that absorbs IR light. This works both for non-polar solvents such as n-heptane and for water non-miscible solvents like chloroform. In a proof of concept study, this approach is applied to monitor a photooxidation of N-phenyl-1,2,3,4-tetrahydroisoquinoline. By using water as an infrared absorbing matrix, analytes, dissolved in non-polar solvents from reactions carried out on a microchip, can be desorbed and ionized for investigation by mass spectrometry.
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Affiliation(s)
- Raphael D Urban
- Institut für Analytische Chemie, Leipzig University, Linnéstraße 3, 04103, Leipzig, Germany
| | - Tillmann G Fischer
- Institut für Organische Chemie, Leipzig University, Johannisallee 29, 04103, Leipzig, Germany
| | - Ales Charvat
- Leibniz-Institut für Oberflächenmodifizierung e.V., Abteilung Funktionale Oberflächen, Permoserstr. 15, 04318, Leipzig, Germany
| | - Konstantin Wink
- Institut für Analytische Chemie, Leipzig University, Linnéstraße 3, 04103, Leipzig, Germany
| | - Benjamin Krafft
- Institut für Analytische Chemie, Leipzig University, Linnéstraße 3, 04103, Leipzig, Germany
| | - Stefan Ohla
- Institut für Analytische Chemie, Leipzig University, Linnéstraße 3, 04103, Leipzig, Germany
| | - Kirsten Zeitler
- Institut für Organische Chemie, Leipzig University, Johannisallee 29, 04103, Leipzig, Germany
| | - Bernd Abel
- Leibniz-Institut für Oberflächenmodifizierung e.V., Abteilung Funktionale Oberflächen, Permoserstr. 15, 04318, Leipzig, Germany
| | - Detlev Belder
- Institut für Analytische Chemie, Leipzig University, Linnéstraße 3, 04103, Leipzig, Germany.
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Prüfert C, Urban RD, Fischer TG, Villatoro J, Riebe D, Beitz T, Belder D, Zeitler K, Löhmannsröben HG. In situ monitoring of photocatalyzed isomerization reactions on a microchip flow reactor by IR-MALDI ion mobility spectrometry. Anal Bioanal Chem 2020; 412:7899-7911. [PMID: 32918557 PMCID: PMC7550389 DOI: 10.1007/s00216-020-02923-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Revised: 08/17/2020] [Accepted: 08/27/2020] [Indexed: 01/21/2023]
Abstract
The visible-light photocatalytic E/Z isomerization of olefins can be mediated by a wide spectrum of triplet sensitizers (photocatalysts). However, the search for the most efficient photocatalysts through screenings in photo batch reactors is material and time consuming. Capillary and microchip flow reactors can accelerate this screening process. Combined with a fast analytical technique for isomer differentiation, these reactors can enable high-throughput analyses. Ion mobility (IM) spectrometry is a cost-effective technique that allows simple isomer separation and detection on the millisecond timescale. This work introduces a hyphenation method consisting of a microchip reactor and an infrared matrix-assisted laser desorption ionization (IR-MALDI) ion mobility spectrometer that has the potential for high-throughput analysis. The photocatalyzed E/Z isomerization of ethyl-3-(pyridine-3-yl)but-2-enoate (E-1) as a model substrate was chosen to demonstrate the capability of this device. Classic organic triplet sensitizers as well as Ru-, Ir-, and Cu-based complexes were tested as catalysts. The ionization efficiency of the Z-isomer is much higher at atmospheric pressure which is due to a higher proton affinity. In order to suppress proton transfer reactions by limiting the number of collisions, an IM spectrometer working at reduced pressure (max. 100 mbar) was employed. This design reduced charge transfer reactions and allowed the quantitative determination of the reaction yield in real time. Among 14 catalysts tested, four catalysts could be determined as efficient sensitizers for the E/Z isomerization of ethyl cinnamate derivative E-1. Conversion rates of up to 80% were achieved in irradiation time sequences of 10 up to 180 s. With respect to current studies found in the literature, this reduces the acquisition times from several hours to only a few minutes per scan.
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Affiliation(s)
- Chris Prüfert
- University of Potsdam, Physical Chemistry, Karl-Liebknecht-Str. 24-25, 14476, Potsdam, Germany.
| | - Raphael David Urban
- Institute of Analytical Chemistry, Leipzig University, Linnéstraße 3, 04103, Leipzig, Germany
| | - Tillmann Georg Fischer
- Institute of Organic Chemistry, Leipzig University, Johannisallee 29, 04103, Leipzig, Germany
| | - José Villatoro
- University of Potsdam, Physical Chemistry, Karl-Liebknecht-Str. 24-25, 14476, Potsdam, Germany
| | - Daniel Riebe
- University of Potsdam, Physical Chemistry, Karl-Liebknecht-Str. 24-25, 14476, Potsdam, Germany
| | - Toralf Beitz
- University of Potsdam, Physical Chemistry, Karl-Liebknecht-Str. 24-25, 14476, Potsdam, Germany
| | - Detlev Belder
- Institute of Analytical Chemistry, Leipzig University, Linnéstraße 3, 04103, Leipzig, Germany
| | - Kirsten Zeitler
- Institute of Organic Chemistry, Leipzig University, Johannisallee 29, 04103, Leipzig, Germany
| | - Hans-Gerd Löhmannsröben
- University of Potsdam, Physical Chemistry, Karl-Liebknecht-Str. 24-25, 14476, Potsdam, Germany.
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Curti C, Battistini L, Sartori A, Zanardi F. New Developments of the Principle of Vinylogy as Applied to π-Extended Enolate-Type Donor Systems. Chem Rev 2020; 120:2448-2612. [PMID: 32040305 PMCID: PMC7993750 DOI: 10.1021/acs.chemrev.9b00481] [Citation(s) in RCA: 101] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Indexed: 12/19/2022]
Abstract
The principle of vinylogy states that the electronic effects of a functional group in a molecule are possibly transmitted to a distal position through interposed conjugated multiple bonds. As an emblematic case, the nucleophilic character of a π-extended enolate-type chain system may be relayed from the legitimate α-site to the vinylogous γ, ε, ..., ω remote carbon sites along the chain, provided that suitable HOMO-raising strategies are adopted to transform the unsaturated pronucleophilic precursors into the reactive polyenolate species. On the other hand, when "unnatural" carbonyl ipso-sites are activated as nucleophiles (umpolung), vinylogation extends the nucleophilic character to "unnatural" β, δ, ... remote sites. Merging the principle of vinylogy with activation modalities and concepts such as iminium ion/enamine organocatalysis, NHC-organocatalysis, cooperative organo/metal catalysis, bifunctional organocatalysis, dicyanoalkylidene activation, and organocascade reactions represents an impressive step forward for all vinylogous transformations. This review article celebrates this evolutionary progress, by collecting, comparing, and critically describing the achievements made over the nine year period 2010-2018, in the generation of vinylogous enolate-type donor substrates and their use in chemical synthesis.
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Affiliation(s)
| | | | | | - Franca Zanardi
- Dipartimento di Scienze degli
Alimenti e del Farmaco, Università
di Parma, Parco Area delle Scienze 27A, 43124 Parma, Italy
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Appun J, Stolz F, Naumov S, Abel B, Schneider C. Modular Synthesis of Dipyrroloquinolines: A Combined Synthetic and Mechanistic Study. J Org Chem 2018; 83:1737-1744. [PMID: 29355317 DOI: 10.1021/acs.joc.7b02466] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A straightforward synthesis of [1,2-a][3',2'-c]dipyrroloquinolines has been developed generating up to eight new σ-bonds and five new stereogenic centers in a simple and modular one-pot operation. Generally good to excellent yields and moderate to good stereoselectivities in favor of the all-cis stereoisomer were observed. A detailed investigation combining synthetic studies, analytical measurements, and theoretical calculations has been conducted to elucidate the reaction mechanism using ESI- and liquid-beam IR-laser desorption mass spectrometry as well as DFT calculations. Key steps of this sequential transformation include a Lewis acid-catalyzed vinylogous Mukaiyama-Mannich reaction of bis(silyl) dienediolate 1 and a Brønsted acid-promoted Mannich-Pictet-Spengler reaction cascade reaction to complete the synthesis of the dipyrroloquinoline core of the target compounds.
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Affiliation(s)
- Johannes Appun
- Institute of Organic Chemistry, University of Leipzig , Johannisallee 29, D-04103 Leipzig, Germany
| | - Ferdinand Stolz
- Leibniz-Institute of Surface Modification (IOM) , Permoserstrasse 15, D-04318 Leipzig, Germany.,Wilhelm-Ostwald-Institute for Physical and Theoretical Chemistry, University of Leipzig , Linnéstrasse 3, D-04103 Leipzig, Germany
| | - Sergej Naumov
- Leibniz-Institute of Surface Modification (IOM) , Permoserstrasse 15, D-04318 Leipzig, Germany
| | - Bernd Abel
- Wilhelm-Ostwald-Institute for Physical and Theoretical Chemistry, University of Leipzig , Linnéstrasse 3, D-04103 Leipzig, Germany
| | - Christoph Schneider
- Institute of Organic Chemistry, University of Leipzig , Johannisallee 29, D-04103 Leipzig, Germany
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Lutze HV, Brekenfeld J, Naumov S, von Sonntag C, Schmidt TC. Degradation of perfluorinated compounds by sulfate radicals - New mechanistic aspects and economical considerations. WATER RESEARCH 2018; 129:509-519. [PMID: 29247911 DOI: 10.1016/j.watres.2017.10.067] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Revised: 10/24/2017] [Accepted: 10/28/2017] [Indexed: 06/07/2023]
Abstract
Perfluorinated organic compounds (PFC) are an important group of pollutants, which are difficult to be degraded in conventional water treatment. Even hydroxyl radical based processes are not capable to degrade these compounds. Sulfate radicals can oxidize a group of PFC, i.e., perfluorinated carboxylic (PFCAs) acids. However, information in literature on kinetics and reaction mechanism is largely based on model simulations which are prone to errors. The present study provides mechanistic insights based on product formation, material balances, competition kinetics experiments and quantum chemical calculations. Furthermore, energy requirements for sulfate radical based degradation of PFCA is evaluated in the present study. PFCAs can be partly mineralized in chain reactions initiated by sulfate radicals (SO4─). The perfluorinated acetic acid (TFA), propionic acid, and butanoic acid are largely degraded in a primary reaction with sulfate radicals. In case of PFCA with a chain length of > 4 carbons low yields of PFCA products were observed. Regarding reaction kinetics sulfate radicals react very slow with PFCAs (≈ 104 M-1 s-1). Thus, the energy demand required for generation of SO4─ by photolysis of S2O82─ (UV/S2O82-) is very high. A 90% degradation of a PFCA by UV/S2O82- was estimated to be 55 kW h m-3 in pure water.
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Affiliation(s)
- Holger V Lutze
- University of Duisburg-Essen, Faculty of Chemistry, Instrumental Analytical Chemistry, Universitätsstraße 5, D-45141, Essen, Germany; IWW Water Centre, Moritzstraße 26, 45476, Mülheim an der Ruhr, Germany; Centre for Water and Environmental Research (ZWU), Universitätsstraße 5, 45141, Essen, Germany.
| | - Julia Brekenfeld
- University of Duisburg-Essen, Faculty of Chemistry, Instrumental Analytical Chemistry, Universitätsstraße 5, D-45141, Essen, Germany
| | - Sergej Naumov
- Leibniz-Institut für Oberflächenmodifizierung e. V., Permoserstr. 15, 04318, Leipzig, Germany
| | - Clemens von Sonntag
- University of Duisburg-Essen, Faculty of Chemistry, Instrumental Analytical Chemistry, Universitätsstraße 5, D-45141, Essen, Germany
| | - Torsten C Schmidt
- University of Duisburg-Essen, Faculty of Chemistry, Instrumental Analytical Chemistry, Universitätsstraße 5, D-45141, Essen, Germany; IWW Water Centre, Moritzstraße 26, 45476, Mülheim an der Ruhr, Germany; Centre for Water and Environmental Research (ZWU), Universitätsstraße 5, 45141, Essen, Germany
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