8 results on '"Anna Codina"'
Search Results
2. Insight into catalyst speciation and hydrogen co-evolution during enantioselective formic acid-driven transfer hydrogenation with bifunctional ruthenium complexes from multi-technique operando reaction monitoring
- Author
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Ian Clegg, Daniel B. G. Berry, John P. Lowe, Catherine L. Lyall, Anna Codina, and Ulrich Hintermair
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Formic acid ,Enantioselective synthesis ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Transfer hydrogenation ,Photochemistry ,01 natural sciences ,0104 chemical sciences ,Catalysis ,chemistry.chemical_compound ,chemistry ,Dehydrogenation ,Physical and Theoretical Chemistry ,0210 nano-technology ,Mesitylene ,Triethylamine ,Acetophenone - Abstract
Transfer hydrogenation of acetophenone from formic acid/triethylamine mixtures catalysed by the Ikariya–Noyori complex [(mesitylene)RuCl(R,R)-(TsDPEN)] has been investigated using simultaneous high-resolution FlowNMR and FlowUV-Vis spectroscopies coupled with on-line sampling head-space mass spectrometry and chiral high-performance liquid chromatography using an integrated, fully automated recirculating flow setup. In line with previous observations, the combined results show a gradual switch from formic acid dehydrogenation to hydrogen transfer mediated by the same Ru-hydride complex, and point to a Ru-formate species as the major catalyst intermediate. Hydrogen bonding in the formic acid/triethylamine mixture emerges as a sensitive 1H NMR probe for the transfer hydrogenation activity of the system and can be used to locate optimum reaction conditions.
- Published
- 2019
3. Kinetic Treatments for Catalyst Activation and Deactivation Processes based on Variable Time Normalization Analysis
- Author
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Michael G. Howlett, Anton Vidal-Ferran, Adam D. Clayton, Carla Alamillo-Ferrer, Richard A. Bourne, Jordi Burés, Ralph W. Adams, Alicia Martínez-Carrión, and Anna Codina
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Normalization (statistics) ,inorganic chemicals ,catalyst deactivation ,Kinetics ,Kinetic analysis ,Variable time ,Kinetic energy ,010402 general chemistry ,01 natural sciences ,Catalysis ,Computational chemistry ,variable time normalization analysis ,Chemistry ,010405 organic chemistry ,organic chemicals ,Communication ,concentration reaction profiles ,General Chemistry ,General Medicine ,Communications ,0104 chemical sciences ,13. Climate action ,kinetics ,Reaction Mechanisms ,catalyst activation - Abstract
Progress reaction profiles are affected by both catalyst activation and deactivation processes occurring alongside the main reaction. These processes complicate the kinetic analysis of reactions, often directing researchers toward incorrect conclusions. We report the application of two kinetic treatments, based on variable time normalization analysis, to reactions involving catalyst activation and deactivation processes. The first kinetic treatment allows the removal of induction periods or the effect of rate perturbations associated with catalyst deactivation from kinetic profiles when the quantity of active catalyst can be measured. The second treatment allows the estimation of the activation or deactivation profile of the catalyst when the order of the reactants for the main reaction is known. Both treatments facilitate kinetic analysis of reactions suffering catalyst activation or deactivation processes.
- Published
- 2019
4. Towards real-time kinetic monitoring of wastewater treatment: A case study of sunlight and ozone treatment of unconcentrated wastewater using flow NMR
- Author
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Amy Jenne, Rajshree Ghosh Biswas, Daniel Lane, Anna Codina, Venita Decker, Myrna J. Simpson, Bing Wu, Daniel H. Lysak, Rudraksha Dutta Majumdar, Ronald Soong, Paul A. Helm, André J. Simpson, Maryam Tabatabaei-Anaraki, and Xiang You
- Subjects
Ozone ,General Chemical Engineering ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Pulp and paper industry ,01 natural sciences ,6. Clean water ,Industrial and Manufacturing Engineering ,0104 chemical sciences ,chemistry.chemical_compound ,Molecular level ,chemistry ,Wastewater ,Environmental Chemistry ,Environmental science ,Degradation (geology) ,Water treatment ,Sewage treatment ,0210 nano-technology ,Ozone generator ,Effluent - Abstract
Wastewater contains complex organic signatures whose components can be harmful to both environmental and human health. Nuclear Magnetic Resonance (NMR) spectroscopy is an excellent tool for molecular monitoring, with the ability to follow total organics, subcategories (aromatics, aliphatic etc.) and, resolution permitting, even individual compounds. However, due to the relatively low sensitivity of NMR, studies of wastewater to date have involved pre-concentration (often many liters) before analysis. This proof of concept study asks, “Is NMR sensitive enough for on-line wastewater monitoring without pre-concentration?” Here, a continuous flow 500 MHz NMR system, coupled with a sunlight simulator and ozone generator, was used on unaltered and unconcentrated wastewater to assess the potential of on-line NMR for understanding wastewater treatment processes. Wastewater from 3 different treatment stages were analyzed. In general, combined ozone and sunlight was more effective at removing organics, while differences in behavior of the same molecules within different wastewater fractions suggest that the chemistry is more complex than just the action of “reactants” (light, ozone) on the target chemicals, and to some extent, involves other components in the wastewater. As such, the nature of the effluent itself could also have important impacts on the rate and completion of its degradation. In summary, on-line NMR of wastewater treatment could be carried out without pre-concentration of the wastewater, in line with important future applications for understanding wastewater treatment processes at the molecular level. Over the last decade, there has been considerable development in low field, low footprint, low cost, NMR spectrometers. Portable versions of those systems could potentially, in the future, be applied for on-site, on-line monitoring of waste streams at water treatment plants, as described here.
- Published
- 2021
5. Revealing the fate of the phenylcoumaran linkage during lignin oxidation reactions
- Author
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Paul C. J. Kamer, Christopher S. Lancefield, Anna Codina, Nicholas J. Westwood, Ciaran W. Lahive, EPSRC, European Commission, University of St Andrews. School of Chemistry, University of St Andrews. EaSTCHEM, and University of St Andrews. Biomedical Sciences Research Complex
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Softwood ,010405 organic chemistry ,Organic Chemistry ,NDAS ,010402 general chemistry ,QD Chemistry ,01 natural sciences ,Biochemistry ,Redox ,0104 chemical sciences ,chemistry.chemical_compound ,chemistry ,Organic chemistry ,Lignin ,Reactivity (chemistry) ,QD ,Physical and Theoretical Chemistry - Abstract
This work was funded by the EP/J018139/1, EP/K00445X/1 grants (N.J.W. and P.C.J.K.), an EPSRC Doctoral Prize Fellowship (C.S.L.), and the European Union (Marie Curie ITN “SuBiCat” PITN-GA-2013-607044, C.W.L., N.J.W., P.C.J.K.). The fate of most lignin linkages, other than the β-O-4, under selective oxidation conditions is largely unknown. In this work we use advanced β-5 lignin model compounds to identify the fate of phenylcoumaran units in a softwood lignin during oxidation with DDQ. By using model compounds combined with detailed characterisation of the oxidised lignin polymer using HSQC and HMBC NMR we show that phenylcoumarones are a major product, and therefore constitute a novel non-native β-5 linkage in oxidised lignins. Additionally, the reactivity of these units in lignin led us to further investigate their connectivity in lignin, showing that they are found as both phenolic and etherified units. The findings and approach developed here will help improve the efficiency of selective oxidative lignin depolymerisation processes, particularly those aimed at the upgrading of softwood lignin in which phenylcoumarans are a major linkage. Postprint
- Published
- 2018
6. Online monitoring of a photocatalytic reaction by real-time high resolution FlowNMR spectroscopy
- Author
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Steven R. Coombes, Matthew Camilleri, Ulrich Hintermair, Anna Codina, Rachael Broomfield-Tagg, David Whittaker, David R. Carbery, Andrew M. R. Hall, and John P. Lowe
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Reaction conditions ,010405 organic chemistry ,Metals and Alloys ,High resolution ,Photocatalytic reaction ,General Chemistry ,010402 general chemistry ,Photochemistry ,01 natural sciences ,Catalysis ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry.chemical_compound ,Primary reaction ,chemistry ,Yield (chemistry) ,Materials Chemistry ,Ceramics and Composites ,Photocatalysis ,Eosin Y ,Spectroscopy - Abstract
We demonstrate how FlowNMR spectroscopy can readily be applied to investigate photochemical reactions that require sustained input of light and air to yield mechanistic insight under realistic conditions. The Eosin Y mediated photo-oxidation of N-allylbenzylamine is shown to produce imines as primary reaction products from which undesired aldehydes form after longer reaction times. Facile variation of reaction conditions during the reaction in flow allows for probe experiments that give information about the mode of action of the photocatalyst.
- Published
- 2017
7. A detailed mechanistic investigation into the reaction of 3-methylpentanoic acid with Meldrum's acid utilizing online NMR spectroscopy
- Author
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Anna L. Dunn, Anna Codina, David A. Foley, Mark T. Zell, and Brian L. Marquez
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Active ingredient ,Reaction mechanism ,Chemical transformation ,010405 organic chemistry ,Dimer ,General Chemistry ,Nuclear magnetic resonance spectroscopy ,010402 general chemistry ,Meldrum's acid ,01 natural sciences ,Chloride ,0104 chemical sciences ,chemistry.chemical_compound ,Nuclear magnetic resonance ,chemistry ,Acyl chloride ,Computational chemistry ,medicine ,General Materials Science ,medicine.drug - Abstract
A thorough investigation into the mechanism of the reaction of 3-methylpentanoic acid and Meldrum's acid using online NMR spectroscopy is reported. This study is an expansion of a previous analysis of this chemical transformation in the synthesis of an active pharmaceutical ingredient imagabalin. The 3-methylpentanoic acid analogue reveals similar behavior under the reaction conditions. Online NMR spectroscopy and offline characterization experiments reveal new information about the mechanism, providing conclusive spectroscopic evidence for the previously hypothesized dimer anhydride intermediate species 3-methylpentanoic anhydride as a productive intermediate. The presence of an acyl chloride intermediate species, 3-methylpentanoyl chloride, is also revealed for the first time in this synthesis. Copyright © 2015 John Wiley & Sons, Ltd.
- Published
- 2015
8. Practical aspects of real-time reaction monitoring using multi-nuclear high resolution FlowNMR spectroscopy
- Author
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Jonathan Chouler, John P. Lowe, Peter Gierth, Andrew M. R. Hall, Ulrich Hintermair, and Anna Codina
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High resolution ,Nanotechnology ,010402 general chemistry ,01 natural sciences ,Data treatment ,Catalysis ,Time reaction ,Analytical Chemistry ,Inorganic Chemistry ,Software ,Process engineering ,Spectroscopy ,Spectrometer ,010405 organic chemistry ,business.industry ,Chemistry ,Process Chemistry and Technology ,0104 chemical sciences ,Chemistry (miscellaneous) ,Temporal resolution ,High field ,business - Abstract
FlowNMR spectroscopy is an excellent technique for non-invasive real-time reaction monitoring under relevant conditions that avoids many of the limitations that bedevil other reaction monitoring techniques. With the recent commercial availability of FlowNMR hard- and software solutions for high resolution spectrometers it is enjoying increased popularity in both academia and industry. We present an account on practical aspects of high field multi-nuclear FlowNMR for reaction monitoring including apparatus design, flow effects, acquisition parameters and data treatment, which are important to consider if accurate kinetic data are to be obtained from FlowNMR experiments. Flow effects on NMR peak areas are particularly important as they can lead to large quantification errors if overlooked, but can easily be corrected for and even used to increase temporal resolution with suitably adjusted instrument settings.
- Published
- 2016
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