The Knoevenagel condensation catalysed by ionic liquids: a mass spectrometric insight into the reaction mechanism

2021 ◽  
Vol 45 (38) ◽  
pp. 17787-17795
Author(s):  
Chiara Salvitti ◽  
Martina Bortolami ◽  
Isabella Chiarotto ◽  
Anna Troiani ◽  
Giulia de Petris
Keyword(s):  
Mass Spectrometry ◽  
Ionic Liquids ◽  
Reaction Mechanism ◽  
Knoevenagel Condensation ◽  
Mass Spectrometric ◽  
Reaction Intermediates ◽  
Insight Into

Mass spectrometry was used to study the Knoevenagel condensation catalysed by imidazolium-based ionic liquids. Two pathways were highlighted by intercepting two different reaction intermediates: a base-catalysed and a carbene-catalysed mechanism.

scholarly journals Identifying reactive intermediates by mass spectrometry

2020 ◽  
Vol 11 (44) ◽  
pp. 11960-11972
Author(s):  
Jaya Mehara ◽  
Jana Roithová
Keyword(s):  
Mass Spectrometry ◽  
Reactive Intermediates ◽  
Reaction Intermediates ◽  
Insight Into ◽  
Structure Properties

Modern approaches of mass spectrometry can identify reaction intermediates and provide a unique insight into their structure, properties and kinetics.

scholarly journals Interaction of ionic liquids with sulfur

2019 ◽  
Vol 484 (2) ◽  
pp. 167-171
Author(s):  
N. P. Tarasova ◽  
Y. O. Mezhuev ◽  
A. A. Zanin ◽  
E. G. Krivoborodov
Keyword(s):  
Mass Spectrometry ◽  
Ionic Liquids ◽  
Reaction Mechanism ◽  
High Resolution ◽  
Chemical Reaction ◽  
Elemental Sulfur ◽  
High Resolution Mass Spectrometry ◽  
Phosphate Anion ◽  
Dimethyl Phosphate ◽  
Resolution Mass

The interaction of tri-n-butylmethylphosphonium dimethylphosphate and 1,3-dimethylimidazolium dimethylphosphate with elemental sulfur in a benzene medium has been described. According to13C and17O NMR and high resolution mass spectrometry, the chemical reaction involves only the dimethyl phosphate anion. The reaction mechanism and the reaction product composition have been proposed.

Enantioselective Reduction Reactions Using Chiral Ionic Liquids: An Overview

2018 ◽  
Vol 15 (5) ◽  
pp. 578-586 ◽  
Author(s):  
Avtar Singh ◽  
Nirmaljeet Kaur ◽  
Harish Kumar Chopra
Keyword(s):  
Ionic Liquids ◽  
Reaction Mechanism ◽  
Reaction Medium ◽  
Reduction Reaction ◽  
Additional Benefit ◽  
Reduction Reactions ◽  
Chiral Ionic Liquids ◽  
Enantioselective Reduction ◽  
Insight Into

Background: Enantioselective reduction reactions play a key role to synthesize compounds of industrial importance. A number of metal and biocatalysts have been developed for their use in this reaction. Chiral ionic liquids (CILs) have been widely used as the reaction medium and the organocatalysts in enantioselective reduction reactions. Objective: This paper focuses on the systematic literature review about the use of chiral ionic liquids (CILs) in the enantioselective reduction reaction. The mechanistic aspects of these species are also taken into account. Conclusion: This review concludes that a number of chiral ionic liquids (CILs) have been successfully employed as the organocatalysts and the reaction medium in the enantioselective reduction reactions. The review also gives an insight into the role of these species in the reaction mechanism. For most of the reactions, chiral ionic liquids provide promising results in terms of yield and enantioselectivity. The recyclability of these chiral moieties from the reaction mixtures offers an additional benefit for the use of these species in asymmetric reactions.

Dynamics of Ion Locking in Doubly Polymerized Ionic Liquids

2020 ◽  
Author(s):  
Swati Arora ◽  
Julisa Rozon ◽  
Jennifer Laaser
Keyword(s):  
Dielectric Constant ◽  
Ionic Liquid ◽  
Ionic Liquids ◽  
Ion Pairs ◽  
Polymer Chains ◽  
Ion Motion ◽  
Charged Species ◽  
Broadband Dielectric Spectroscopy ◽  
Covalently Linked ◽  
Insight Into

<div>In this work, we investigate the dynamics of ion motion in “doubly-polymerized” ionic liquids (DPILs) in which both charged species of an ionic liquid are covalently linked to the same polymer chains. Broadband dielectric spectroscopy is used to characterize these materials over a broad frequency and temperature range, and their behavior is compared to that of conventional “singly-polymerized” ionic liquids (SPILs) in which only one of the charged species is attached to the polymer chains. Polymerization of the DPIL decreases the bulk ionic conductivity by four orders of magnitude relative to both SPILs. The timescales for local ionic rearrangement are similarly found to be approximately four orders of magnitude slower in the DPILs than in the SPILs, and the DPILs also have a lower static dielectric constant. These results suggest that copolymerization of the ionic monomers affects ion motion on both the bulk and the local scales, with ion pairs serving to form strong physical crosslinks between the polymer chains. This study provides quantitative insight into the energetics and timescales of ion motion that drive the phenomenon of “ion locking” currently under investigation for new classes of organic electronics.</div>

Confounding contaminants in mass spectrometric reaction monitoring

2018 ◽  
Author(s):  
Gilian T. Thomas ◽  
Landon MacGillivray ◽  
Natalie L. Dean ◽  
Rhonda L. Stoddard ◽  
Lars Yunker ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Mass Spectrometric ◽  
Negative Ion ◽  
Reaction Monitoring ◽  
Schlenk Flask ◽  
Dynamic Analyses ◽  
Rubber Septa ◽  
Negative Ion Mode ◽  
Mode A

<p>Reactions carried out in the presence of rubber septa run the risk of additives being leached out by the solvent. Normally, such species are present at low enough levels that they do not interfere with the reaction significantly. However, when studying reactions using sensitive methods such as mass spectrometry, the appearance of even trace amounts of material can confuse dynamic analyses of reactions. A wide variety of additives are present in rubber along with the polymer: antioxidants, dyes, detergent, and vulcanization agents, and these are all especially problematic in negative ion mode. A redesigned Schlenk flask for pressurized sample infusion (PSI) is presented as a means of practically eliminating the presence of contaminants during reaction analyses.</p>

Resolution of a protein sequence ambiguity by X-ray crystallographic and mass spectrometric methods

1992 ◽  
Vol 25 (2) ◽  
pp. 205-210 ◽  
Author(s):  
L. J. Keefe ◽  
E. E. Lattman ◽  
C. Wolkow ◽  
A. Woods ◽  
M. Chevrier ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Amino Acid ◽  
Electron Density ◽  
Mass Spectrometric ◽  
Amino Acid Sequences ◽  
Data Matrix ◽  
Protein Crystal ◽  
Insertion Mutant ◽  
Laser Desorption Mass Spectrometry ◽  
X Ray

Ambiguities in amino acid sequences are a potential problem in X-ray crystallographic studies of proteins. Amino acid side chains often cannot be reliably identified from the electron density. Many protein crystal structures that are now being solved are simple variants of a known wild-type structure. Thus, cloning artifacts or other untoward events can readily lead to cases in which the proposed sequence is not correct. An example is presented showing that mass spectrometry provides an excellent tool for analyzing suspected errors. The X-ray crystal structure of an insertion mutant of Staphylococcal nuclease has been solved to 1.67 Å resolution and refined to a crystallographic R value of 0.170 [Keefe & Lattman (1992). In preparation]. A single residue has been inserted in the C-terminal α helix. The inserted amino acid was believed to be an alanine residue, but the final electron density maps strongly indicated that a glycine had been inserted instead. To confirm the observations from the X-ray data, matrix-assisted laser desorption mass spectrometry was employed to verify the glycine insertion. This mass spectrometric technique has sufficient mass accuracy to detect the methyl group that distinguishes glycine from alanine and can be extended to the more common situation in which crystallographic measurements suggest a problem with the sequence, but cannot pinpoint its location or nature.

scholarly journals The apple C2H2-type zinc finger transcription factor MdZAT10 positively regulates JA-induced leaf senescence by interacting with MdBT2

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Kuo Yang ◽  
Jian-Ping An ◽  
Chong-Yang Li ◽  
Xue-Na Shen ◽  
Ya-Jing Liu ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Transcription Factor ◽  
Liquid Chromatography ◽  
Zinc Finger ◽  
Leaf Senescence ◽  
Transcriptional Activity ◽  
Molecular Mechanisms ◽  
Liquid Chromatography Mass Spectrometry ◽  
Zinc Finger Transcription Factor ◽  
Insight Into

AbstractJasmonic acid (JA) plays an important role in regulating leaf senescence. However, the molecular mechanisms of leaf senescence in apple (Malus domestica) remain elusive. In this study, we found that MdZAT10, a C2H2-type zinc finger transcription factor (TF) in apple, markedly accelerates leaf senescence and increases the expression of senescence-related genes. To explore how MdZAT10 promotes leaf senescence, we carried out liquid chromatography/mass spectrometry screening. We found that MdABI5 physically interacts with MdZAT10. MdABI5, an important positive regulator of leaf senescence, significantly accelerated leaf senescence in apple. MdZAT10 was found to enhance the transcriptional activity of MdABI5 for MdNYC1 and MdNYE1, thus accelerating leaf senescence. In addition, we found that MdZAT10 expression was induced by methyl jasmonate (MeJA), which accelerated JA-induced leaf senescence. We also found that the JA-responsive protein MdBT2 directly interacts with MdZAT10 and reduces its protein stability through ubiquitination and degradation, thereby delaying MdZAT10-mediated leaf senescence. Taken together, our results provide new insight into the mechanisms by which MdZAT10 positively regulates JA-induced leaf senescence in apple.

Vitamin D analyses in veterinary feeds by gas chromatography-tandem mass spectrometry

2021 ◽  
pp. 146906672110002
Author(s):  
Andreas Lehner ◽  
Margaret Johnson ◽  
Alan Zimmerman ◽  
Justin Zyskowski ◽  
John Buchweitz
Keyword(s):  
Mass Spectrometry ◽  
Vitamin D ◽  
Gas Chromatography ◽  
Liquid Chromatography ◽  
Tandem Mass Spectrometry ◽  
Vitamin D3 ◽  
Mass Spectrometric ◽  
Chromatographic Behavior ◽  
Tandem Mass ◽  
Chromatography Tandem Mass Spectrometry

This report examines the feasibility of determination of Vitamin D3, D2 and their 25-hydroxy metabolites utilizing Gas Chromatography Tandem Mass Spectrometry (GC/MS/MS) as a potential alternative to popular Liquid Chromatography Tandem Mass Spectrometric (LC/MS/MS) methodologies. The GC/MS/MS approach was found to operate reasonably well despite long-standing concerns that gas-liquid chromatography of vitamin D compounds invoke thermal rearrangements owing to the relatively high inlet and capillary column temperatures used. The workup procedure involved incubation of feed samples with concentrated potassium hydroxide for overnight fat saponification, extraction of D Vitamins in n-hexane and reaction with N,O-bis(trimethylsilyl)trifluoroacetamide at 70 °C for 30 mins. In addition to parent compounds, small amounts of pyro-, isopyro-, and iso-vitamin D and isotachysterol3 variants were obtained from each Vitamin D-related compound upon extraction and GC/MS/MS analysis. Mass spectral and chromatographic behavior of these compounds are herein described and interpreted. Multiple Reaction Monitoring settings on GC/MS/MS included m/z 456→351 for Vitamin D3 and m/z 486→363 for Vitamin D2. Trimethylsilylation enabled single predominant peaks for Vitamins D3 and D2, and sample workup in the presence of deuterated Vitamin D analogs enabled accurate and precise sensitivity to 1 ppb (ng/g) in feeds. The method could be extended with reasonable accuracy to 25-hydroxy (25OH) compounds, but accuracies would be significantly improved by inclusion of respective 25OH-specific deuterated internal standards. The method was applied to 27 submissions of suspect dog foods of which 22% were discovered elevated and 44% were discovered to contain toxic levels of Vitamin D3. The described method was thus discovered to provide a suitable mass spectrometric approach for Vitamin D, proving itself here specifically of value in detection of ergocalciferol and cholecalciferol in animal feeds. The specificity and sensitivity of the tandem quadrupole approach can enable suitable applicability to serum determination if desired.

In situ loading of well-dispersed silver nanoparticles on nanocrystalline magnesium oxide for real-time monitoring of catalytic reactions by surface enhanced Raman spectroscopy

Nanoscale ◽  
2015 ◽  
Vol 7 (40) ◽  
pp. 16952-16959 ◽  
Author(s):  
Kaige Zhang ◽  
Gongke Li ◽  
Yuling Hu
Keyword(s):  
Raman Spectroscopy ◽  
Surface Enhanced Raman Spectroscopy ◽  
Catalytic Reactions ◽  
Reaction Intermediates ◽  
Reaction Conditions ◽  
Surface Enhanced ◽  
Surface Enhanced Raman ◽  
Nanocrystalline Magnesium Oxide ◽  
Insight Into

The surface-enhanced Raman spectroscopy (SERS) technique is of great importance for insight into the transient reaction intermediates and mechanistic pathways involved in heterogeneously catalyzed chemical reactions under actual reaction conditions, especially in water.

scholarly journals Quantitative imaging mass spectrometry of renal sulfatides: validation by classical mass spectrometric methods

2014 ◽  
Vol 55 (11) ◽  
pp. 2343-2353 ◽  
Author(s):  
Christian Marsching ◽  
Richard Jennemann ◽  
Raphael Heilig ◽  
Hermann-Josef Gröne ◽  
Carsten Hopf ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Quantitative Imaging ◽  
Imaging Mass Spectrometry ◽  
Mass Spectrometric
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