“Impossible” Chemistries Based on Flow and Micro
Total Page:16
File Type:pdf, Size:1020Kb
Load more
Recommended publications
-
Reactivity and Mechanism of the Reactions in Volving Carbonyl Ylide
Bull, i Korean Chem. Soc.t Vol. 14, No. 1, 1993 149 10. 0. Inganas, R. Erlandsson, C. Nylander, and I. Lunds- eration of other types of ylides.6 Even though many studies trom, J. Phys. Chem. Solids, 45, 427 (1984). have been reported for the intermediates of carbonyl ylides 11. P. Novak, B. Rasch, and W. Vielstich, J. Electro사 诚m Soc., in the reactions of carbenes with a carbonyl oxygens,7 the 138, 3300 (1991). reactions are limited to the discussion of the transition metal 12. K. M. Cheung, D. Bloor, and G. C. Stevens, Polymers, catalyzed decomposition of a diazo compounds in the prese 29, 1709 (1988). nce of a carbonyl group. In this paper we report the reactivity and mechanism of the reactions involving carbonyl ylide intermediate from the photolytic kinetic results of non-catalytic decompositions of diazomethane and diphenyldiazomethane in the presence of a carbonyl group. Reactivity and Mechanism of the Reactions In volving Carbonyl Ylide Intermediate Experimentals Dae Dong Sung*, Kyu Chui Kim, Sang Hoon Lee, General Photolysis Conditions. Diazomethane was and Zoon Ha Ryu* generated by Aldrich MNNG Diazald apparatus as follows.8 1 mmol of l-methyl-3-nitro-l-nitrosoguanidine (MNNG) is Department of Chemistry, placed in the inside tube of. the Diazald kit through its screw Dong-A University, Pusan 604-714 cap opening along with 0.5 mL of water of dissipate any ^Department of Chemistry, heat generated. 3 mL of diethyl ether is placed in the outside Dong-Eui University, Pusan 614-010 tube and the two parts are assembled with a butyl "O”-ring and held with a pinch-type clamp. -
Design and Engineering of Microreactor and Smart-Scaled Flow Processes
Editorial Special Issue : Design and engineering of microreactor and smart-scaled flow processes Citation for published version (APA): Hessel, V. (2015). Editorial Special Issue : Design and engineering of microreactor and smart-scaled flow processes. Processes, 3(1), 19-22. https://doi.org/10.3390/pr3010019 DOI: 10.3390/pr3010019 Document status and date: Published: 01/01/2015 Document Version: Publisher’s PDF, also known as Version of Record (includes final page, issue and volume numbers) Please check the document version of this publication: • A submitted manuscript is the version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website. • The final author version and the galley proof are versions of the publication after peer review. • The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal. -
Free Radical Reactions (Read Chapter 4) A
Chemistry 5.12 Spri ng 2003, Week 3 / Day 2 Handout #7: Lecture 11 Outline IX. Free Radical Reactions (Read Chapter 4) A. Chlorination of Methane (4-2) 1. Mechanism (4-3) B. Review of Thermodynamics (4-4,5) C. Review of Kinetics (4-8,9) D. Reaction-Energy Diagrams (4-10) 1. Thermodynamic Control 2. Kinetic Control 3. Hammond Postulate (4-14) 4. Multi-Step Reactions (4-11) 5. Chlorination of Methane (4-7) Suggested Problems: 4-35–37,40,43 IX. A. Radical Chlorination of Methane H heat (D) or H H C H Cl Cl H C Cl H Cl H light (hv) H H Cl Cl D or hv D or hv etc. H C Cl H C Cl H Cl Cl C Cl H Cl Cl Cl Cl Cl H H H • Why is light or heat necessary? • How fast does it go? • Does it give off or consume heat? • How fast are each of the successive reactions? • Can you control the product ratio? To answer these questions, we need to: 1. Understand the mechanism of the reaction (arrow-pushing!). 2. Use thermodynamics and kinetics to analyze the reaction. 1 1. Mechanism of Radical Chlorination of Methane (Free-Radical Chain Reaction) Free-radical chain reactions have three distinct mechanistic steps: • initiation step: generates reactive intermediate • propagation steps: reactive intermediates react with stable molecules to generate other reactive intermediates (allows chain to continue) • termination step: side-reactions that slow the reaction; usually combination of two reactive intermediates into one stable molecule Initiation Step: Cl2 absorbs energy and the bond is homolytically cleaved. -
Photoionization Studies of Reactive Intermediates Using Synchrotron
Photoionization Studies of Reactive Intermediates using Synchrotron Radiation by John M.Dyke* School of Chemistry University of Southampton SO17 1BJ UK *e-mail: [email protected] 1 Abstract Photoionization of reactive intermediates with synchrotron radiation has reached a sufficiently advanced stage of development that it can now contribute to a number of areas in gas-phase chemistry and physics. These include the detection and spectroscopic study of reactive intermediates produced by bimolecular reactions, photolysis, pyrolysis or discharge sources, and the monitoring of reactive intermediates in situ in environments such as flames. This review summarises advances in the study of reactive intermediates with synchrotron radiation using photoelectron spectroscopy (PES) and constant-ionic-state (CIS) methods with angular resolution, and threshold photoelectron spectroscopy (TPES), taking examples mainly from the recent work of the Southampton group. The aim is to focus on the main information to be obtained from the examples considered. As future research in this area also involves photoelectron-photoion coincidence (PEPICO) and threshold photoelectron-photoion coincidence (TPEPICO) spectroscopy, these methods are also described and previous related work on reactive intermediates with these techniques is summarised. The advantages of using PEPICO and TPEPICO to complement and extend TPES and angularly resolved PES and CIS studies on reactive intermediates are highlighted. 2 1.Introduction This review is organised as follows. After an Introduction to the study of reactive intermediates by photoionization with fixed energy photon sources and synchrotron radiation, a number of Case Studies are presented of the study of reactive intermediates with synchrotron radiation using angle resolved PES and CIS, and TPE spectroscopy. -
Trapping and Spectroscopic Characterization of an Fe -Superoxo
Trapping and spectroscopic characterization of an FeIII-superoxo intermediate from a nonheme mononuclear iron-containing enzyme Michael M. Mbughunia, Mrinmoy Chakrabartib, Joshua A. Haydenb, Emile L. Bominaarb, Michael P. Hendrichb, Eckard Münckb, and John D. Lipscomba,1 aDepartment of Biochemistry, Molecular Biology and Biophysics, and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, MN 55455, and bDepartment of Chemistry, Carnegie Mellon University, Pittsburgh, PA 15213 Edited by Edward I. Solomon, Stanford University, Stanford, CA, and approved August 4, 2010 (received for review July 9, 2010) III •− Fe -O2 intermediates are well known in heme enzymes, but none have been characterized in the nonheme mononuclear FeII enzyme family. Many steps in the O2 activation and reaction cycle of FeII-containing homoprotocatechuate 2,3-dioxygenase are made detectable by using the alternative substrate 4-nitrocatechol (4NC) and mutation of the active site His200 to Asn (H200N). Here, the first intermediate (Int-1) observed after adding O2 to the H200N- 4NC complex is trapped and characterized using EPR and Möss- ∕ III bauer (MB) spectroscopies. Int-1 is a high-spin (S1 ¼ 5 2) Fe anti- ∕ ≈ −1 ferromagnetically (AF) coupled to an S2 ¼ 1 2 radical (J 6cm in H • ¼ JS1 S2). It exhibits parallel-mode EPR signals at g ¼ 8.17 from the S ¼ 2 multiplet, and g ¼ 8.8 and 11.6 from the S ¼ 3 multiplet. 17 These signals are broadened significantly by O2 hyperfine inter- ≈ III •− actions (A17O 180 MHz). Thus, Int-1 is an AF-coupled Fe -O2 spe- cies. The experimental observations are supported by density functional theory calculations that show nearly complete transfer of spin density to the bound O2. -
Tr2013 03 Flow Chemistry.Pdf
What is flow chemistry? Flow chemistry is a process in which a reaction is run Continuously in a flowing stream rather than in batch production Comparison between traditional chemistry and flow chemistry Reaction Stoichiometry: In traditional chemistry this is defined by the concentration of chemical reagents and their volumetric ratio. In flow chemistry this is defined by The concentration of the chemical reagents and the ratio of their flow rate Residence time: In traditional chemistry this is determined by how long a vessel is kept at given temperature. In flow the volumetric residence time is used given by the ratio of the volume of the reactor and the overall flow rate What is residence time? Residence time of a reagent is defined as the amount of time that the reaction is cooled or heated. Residence time = reactor volume/flow rate Continuous flow reactors: a perspective Advantages: 1. Improved thermal management 2. Mixing control 3. Application of the extreme reaction conditions Principles of green chemistry: 1. Prevention of waste O NH HO 2 OH N Solvent -free O reaction temp : 65 oC reaction time : 5.1 min yield : 91% Green chem., 2012, 14, 38-54 2. Atom economy O OH toluene reaction temp : 240 oC pressure : 100 bar yield : 95% O H O O O MeCN O H O reaction temp : 60 oC Green chem., 2012, 14, 38-54 O O N N N N O N O O N O H N electon-withdrawing group O CCl3 Cl O Smallest unit of benzylimidate NaOH (3.4 eq) N N BnOH (7.8 eq) N N o Cl N Cl 0 to 50 C, 2.5 h O N O 81% Org. -
The Fundamentals Behind the Use of Flow Reactors in Electrochemistry
The fundamentals behind the use of flow reactors in electrochemistry Citation for published version (APA): Noël, T., Cao, Y., & Laudadio, G. (2019). The fundamentals behind the use of flow reactors in electrochemistry. Accounts of Chemical Research, 52(10), 2858-2869. https://doi.org/10.1021/acs.accounts.9b00412 DOI: 10.1021/acs.accounts.9b00412 Document status and date: Published: 01/10/2019 Document Version: Publisher’s PDF, also known as Version of Record (includes final page, issue and volume numbers) Please check the document version of this publication: • A submitted manuscript is the version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website. • The final author version and the galley proof are versions of the publication after peer review. • The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal. -
Photochemistry of S-Alkoxy Dibenzothiphenium Tetrafluoroborates, N-Alkoxy Pyridinium Perchlorates, and Sulfonium Ylides
Iowa State University Capstones, Theses and Graduate Theses and Dissertations Dissertations 2020 Photochemical generation of electron poor reactive intermediates: Photochemistry of S-alkoxy dibenzothiphenium tetrafluoroborates, N-alkoxy pyridinium perchlorates, and Sulfonium ylides Jagadeesh Kolattoor Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/etd Recommended Citation Kolattoor, Jagadeesh, "Photochemical generation of electron poor reactive intermediates: Photochemistry of S-alkoxy dibenzothiphenium tetrafluoroborates, N-alkoxy pyridinium perchlorates, and Sulfonium ylides" (2020). Graduate Theses and Dissertations. 18341. https://lib.dr.iastate.edu/etd/18341 This Thesis is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Graduate Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. Photochemical generation of electron poor reactive intermediates: Photochemistry of S- alkoxy dibenzothiophenium tetrafluoroborates, N-alkoxy pyridinium perchlorates, and Sulfonium ylides by Jagadeesh Kolattoor A dissertation submitted to the graduate faculty in partial fulfillment of requirements for the degree of DOCTOR OF PHILOSOPHY Major: Organic Chemistry Program of Study Committee: William S. Jenks, Major Professor Arthur Winter Brett VanVeller Igor Slowing Marek Pruski The student author, whose presentation of the scholarship herein was approved by the program of study committee, is solely responsible for the content of this dissertation. The Graduate College will ensure this dissertation is globally accessible and will not permit alterations after a degree is conferred. Iowa State University Ames, Iowa 2020 Copyright © Jagadeesh Kolattoor, 2020. All rights reserved. -
Introduction to Alkenes and Alkynes in an Alkane, All Covalent Bonds
Introduction to Alkenes and Alkynes In an alkane, all covalent bonds between carbon were σ (σ bonds are defined as bonds where the electron density is symmetric about the internuclear axis) In an alkene, however, only three σ bonds are formed from the alkene carbon -the carbon thus adopts an sp2 hybridization Ethene (common name ethylene) has a molecular formula of CH2CH2 Each carbon is sp2 hybridized with a σ bond to two hydrogens and the other carbon Hybridized orbital allows stronger bonds due to more overlap H H C C H H Structure of Ethylene In addition to the σ framework of ethylene, each carbon has an atomic p orbital not used in hybridization The two p orbitals (each with one electron) overlap to form a π bond (p bonds are not symmetric about the internuclear axis) π bonds are not as strong as σ bonds (in ethylene, the σ bond is ~90 Kcal/mol and the π bond is ~66 Kcal/mol) Thus while σ bonds are stable and very few reactions occur with C-C bonds, π bonds are much more reactive and many reactions occur with C=C π bonds Nomenclature of Alkenes August Wilhelm Hofmann’s attempt for systematic hydrocarbon nomenclature (1866) Attempted to use a systematic name by naming all possible structures with 4 carbons Quartane a alkane C4H10 Quartyl C4H9 Quartene e alkene C4H8 Quartenyl C4H7 Quartine i alkine → alkyne C4H6 Quartinyl C4H5 Quartone o C4H4 Quartonyl C4H3 Quartune u C4H2 Quartunyl C4H1 Wanted to use Quart from the Latin for 4 – this method was not embraced and BUT has remained Used English order of vowels, however, to name the groups -
Chem 51B Chapter 15 Notes
Lecture Notes Chem 51B S. King Chapter 15 Radical Reactions I. Introduction A radical is a highly reactive intermediate with an unpaired electron. Radicals are involved in oxidation reactions, combustion reactions, and biological reactions. Structure: compare with: compare with: Stability: Free radicals and carbocations are both electron deficient and they follow a similar order of stability: R R H H , > R C > R C > R C > H C R H H H • like carbocations, radicals can be stabilized by resonance. H H H H C C C C H C CH3 H C CH3 H H • unlike carbocations, no rearrangements are observed in free radical reactions. Q. How are free radicals formed? A. Free radicals are formed when bonds break homolytically: 103 Look @ the arrow pushing: Notice the fishhook arrow! It shows movement of a single electron: Compare with heterolytic bond cleavage: A double-headed arrow shows movement of a pair of electrons: Nomenclature: bromide ion bromine atom Bromine (molecule) II. General Features of Radical Reactions Radicals are formed from covalent bonds by adding energy in the form of heat or light (hν). Some radical reactions are carried out in the presence of radical initiators, which contain weak bonds that readily undergo homolysis. The most common radical initiators are peroxides (ROOR), which contain the weak O−O bond. A. Common Reactions of Radicals: Radicals undergo two common reactions: they react with σ-bonds and they add to π-bonds. 1. Reaction of a Radical X• with a C−H bond A radical X• abstracts a H atom from a C−H bond to form H−X and a carbon radical: 104 2. -
Towards More Efficient, Greener Syntheses Through Flow Chemistry
Towards More Efficient, Greener Syntheses through Flow Chemistry The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters. Citation Lummiss, Justin A.M. et al. “Towards More Efficient, Greener Syntheses through Flow Chemistry.” The Chemical Record 17, 7 (February 2017): 667–680 © 2017 Wiley-Verlag As Published https://doi.org/10.1002/tcr.201600139 Publisher Wiley Blackwell Version Author's final manuscript Citable link http://hdl.handle.net/1721.1/114543 Terms of Use Creative Commons Attribution-Noncommercial-Share Alike Detailed Terms http://creativecommons.org/licenses/by-nc-sa/4.0/ PERSONAL ACCOUNT Alternatively, entire flow systems with specialized attachments Towards More Efficient, can be purchased from various commercial suppliers.[4b] Greener Syntheses Through Flow Chemistry Justin A.M. Lummiss,[a] Peter D. Morse,[a] Rachel L. Beingessner,[a] and Timothy F. Jamison*[a] Abstract: Technological advances have an important role in the design of greener synthetic processes. In this Personal Account, we describe a wide range of thermal, photochemical, catalytic, and biphasic chemical transformations examined by our group. Each of these demonstrate how the merits of a continuous flow synthesis platform can align with some of the goals put forth by the Twelve Principles of Green Chemistry. In particular, we illustrate the potential for improved reaction efficiency in terms of atom economy, product yield and reaction rates, the ability to design synthetic process with chemical and solvent waste reduction in mind as well as highlight the benefits of the real- time monitoring capabilities in flow for highly controlled synthetic output. -
Flow Chemistry
Flow chemistry Flow chemistry is also known as continuous flow or plug flow chemistry. It involves a chemical reaction run in a continuous flow stream. The process offers potential for the efficient manufacture of chemical products. Recent breakthroughs using Vapourtec systems are in production of Tamoxifen (Breast Cancer) and Artemisinin (Malaria). Reactants are first pu mped into a mixing device. Flow continues through a temperature controlled reactor until the reaction is complete. The reactor can be a simple pipe, tube or complex micro-structured device. The mixing device and reactor are maintained at the temperature to promote the desired reaction. The reactants may also be exposed to an electrical flux or a photon flux to promote an electrochemical or photochemical reaction. Click here for examples of flow chemistry performed in Vapourtec systems Flow chemistry differs from conventional batch chemistry by having the following important features: Flow of reagents In Flow chemistry reagents are pumped under pressure and flow continuously through the reactor. This contrasts with batch reactors where all reagents are loaded into a vessel at the start https://www.vapourtec.com Control of reaction time Reaction time is determined by the time the reagents take to flow through the reactor. This period is called the residence time. Control of stoichiometry Reaction stoichiometry is controlled by the relative flow rates of the reactants. The concentration of one reagent relative to another can be increased simply by pumping that reagent at a higher rate of flow. Heat transfer Flow reactors have excellent heat transfer when compared with batch reactors. This feature is due to the much greater surface area to volume ratio of flow reactors over batch reactors.