DOCSLIB.ORG

The Dichlorocyclopropanation of 3-Methyl-1-Cyclohexene and 4-Vinyl-1- Cyclohexene Using Water Soluble Multi-Site Phase Transfer Catalyst-A Kinetic Study

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The Dichlorocyclopropanation of 3-Methyl-1-Cyclohexene and 4-Vinyl-1- Cyclohexene Using Water Soluble Multi-Site Phase Transfer Catalyst-A Kinetic Study Int.J.Curr.Microbiol.App.Sci (2014) 3(9) 211-223 ISSN: 2319-7706 Volume 3 Number 9 (2014) pp. 211-223 http://www.ijcmas.com Original Research Article The dichlorocyclopropanation of 3-methyl-1-cyclohexene and 4-vinyl-1- cyclohexene using water soluble multi-site phase transfer catalyst-A kinetic study K.Shanmugam* and E.Kannadasan Deptartment of Chemistry, Government Arts College, Chidambaram, TamilNadu, India *Corresponding author A B S T R A C T The present study focuses the attention towards the utility of multi-site phase K e y w o r d s transfer catalyst (MPTC), is demonstrated by studying hydroxide-ion initiated reaction like dichlorocarbene addition to olefins. The formation of the product was Multi-site phase monitored by GLC.Dichlorocyclopropanation of 3-methyl-1-cyclohexene and 4- transfer catalysts, vinyl-1-cyclohexene catalysed by multi-site phase transfer catalyst carried out in Dichlorocyclopro biphasic medium under pseudo-first-order conditions by keeping aqueous sodium panation, hydroxide and chloroform in excess. The effect of various experimental parameters 3-methyl-1- on the rate of the reaction has been studied. Also thermodynamic parameters such cyclohexene;4- as S#, G# and H# were evaluated; based on the experimental results, a suitable vinyl-1- mechanism is proposed.It also deals in greater detail on the kinetic aspects of cyclohexene, Kinetics chosen reactions. An attempt has been made to compare the ability of MPTC-1 with MPTC-II and single-site PTC for dichlorocarbeneaddition to olefins like 3- methyl-l-cyclohexene and 4-vinyl-l-cyclohexene. Introduction The reaction of chloroform with strong to be generated in, or transferred to the bases to generate synthetically useful organic phase, where its reaction with 3- dichlorocarbene normally requires methyl-l-cyclohexene is much greater than anhydrous conditions to avoid its rapid with water addition of dichlorocarbene to 3- hydrolysis (Reeves et al., 1976). Thus methyl-l-cyclohexene gave only normal addition of chloroform to a mixture of 3- dichlorocyclopropane product. Makosza and methyl-l-cyclohexene and aqueous 25% Bialecka (1977) formulated the mechanism sodium hydroxide solution gives 60-70% of the olefin (cyclohexene) yield in the presence of a phase transfer dichlorocyclopropanation under phase catalyst such as tridecyl methyl ammonium transfer conditions as reaction of CHCl3 chloride or benzyl triethyl ammonium with OH- at the aqueous organic phase chloride. The remarkable increase in yield of boundary, from where it is then taken in to the dechlorocarbene adduct reflects the the organic phase by the quaternary cation. ability of the quaternary salt to cause :CCl2 Soluble phase transfer catalysts for 211 Int.J.Curr.Microbiol.App.Sci (2014) 3(9) 211-223 dichlorocarbene addition to cyclohexene bicyclo[4.1.0]-heptane derivatives by the with concentrated aqueous sodium addition of dichlorocarbene to 3-methyl-l- hydroxide as the base were first reported by cyclohexene; the method involves the von Doering et al., 1980 and were reaction of 3-methyl-l-cyclohexene with investigated in detail by Makosza, 1978. The chloroform in the presence of concentrated phase transfer catalyzed dichlorocarbene aqueous solution of sodium hydroxide addition reaction of 3-methyl-l-cyclohexene (15%w/w) and catalytic amount of MPTC-I. was thought to proceed by rate-limiting The reaction proceeds exothermically when generation of the dichlorocarbene and the reagents are mixed at 500C and the hydroxide ion at the aqueous / organic yields of the product obtained by this interface. method are very high usually about 100%, within one hour with no excess of the 3- The reaction of chloroform with 4-vinyl-l- methyl-l-cyclohexene required. The ratio of cyclohexene (Starks and Napier, 1976) in 3-methyl-l-cyclohexene to chloroform the presence of sodium hydroxide gives an applied is 1: 10 in volume, depending on the excellent yield of a product C9H12Cl2which availability of the olefin. In a similar way, contains the bicyclo [4.1.0] heptane the addition of dichlorocarbene with 4- (norcarane) skeleton. In the early work, we vinyl-1-cyclohexene yielded 100% product have observed that dichlorocarbene addition within one hour under PTC conditions. reaction was carried out with excess of 3- methyl-l-cyclohexene; dichloronorcarane The dichlorocarbene addition with 3-methyl- product was obtained in a yield of about l-cyclohexene and with 4-vinyl-l- 63% under single-site PTC conditions. The cyclohexene were chosen to investigate the present detailed investigation of this reaction kinetic aspects using the new, water-soluble permitted us to develop a new method for multi-site phase transfer catalyst (MPTC- the preparation of 7,7 dichloro-3-methyl- I). CH3 H3C MPTC-I (0.1 mol%) Cl CHCl3, 15% NaOH, 500rpm, 500C Cl 7,7'-dichloro-3-methyl-bicyclo[4.1.0]-heptane (Scheme-1) MPTC(0.1 mol%) Cl CHCl , 15% NaOH, 3 Cl 500rpm, 500C 7,7'-dichloro-4-vinyl-bicyclo[4.1.0]-heptane (Scheme-2) Dichlorocarbine addition to 3-methyl-l-cyclohexene and 4-vinyl-l-cyclohexene under PTC conditions 212 Int.J.Curr.Microbiol.App.Sci (2014) 3(9) 211-223 The kinetic experiments for the 89%. This reaction was also carried out by dichlorocarbene addition to 3-methyl-l- Winberg et al, 2007, using 50% aqueous cyclohexene and 4-vinyl-l-cyclohexene sodium hydroxide and catalytic amount of (schemes 1, 2) were conducted under bi- TEBA (PTC) and obtained 72% yield of the phase conditions with excess of aqueous norcarane product, 7, 7 dichlorobicylo sodium hydroxide and chloroform under [4.1.0]-heptane.In the present study, the rate pseudo first order conditions. The reaction constant is dependent on the stirring speed was studied at a stirring speed of 500rpm in up to 500rpm and maintains constancy the temperature range 40-600C. Before the beyond the limit. The reaction is carried out kinetic run was started, the catalyst was in aqueous medium; the anion exchange conditioned with aqueous sodium hydroxide equilibrium between the anions in the and chloroform for 10 minutes. The aqueous phase and those associated with substrate, 3-methyl-l-cyclohexene/4-vinyl-l- quaternary salt in the organic phase was cyclohexene preheated at the appropriate very relative to the organic phase temperature, was added to the reaction transformation reaction. The mass transfer mixture. The samples were collected from across the interface is regarded as evident the organic layer at regular intervals of time. from Fig. 1 at low stirring speed. At The kinetics of dichlorocarbene was agitation level 500rpm, anion exchange followed by estimating the formation of two equilibrium is very fast relative to the different norcarane products namely 7,7 - reaction and the substrate consumption rate dichloro-3-methyl-bicyclo[4.1.0]-heptane becomes independent of the stirring rate as and 7,7 dichloro-4-vinyl-bicyclo[4.1.0]- observed by Makoszaet al, 1975,, in the heptane using gas chromatographic study of dichlorocarbene addition to technique. The effect of various cyclohexene catalyzed by triethyl benzyl experimental parameters such as stirring ammonium chloride (TEBA) under PTC speed, substrate concentration, sodium conditions. Doering, Wawrzyniewicz and hydroxide concentration and temperature on Jawdosiak, 1985 reported independently a the reaction rate constants were studied. The similar observation that reflected kinetic kinetics was measured up to 30% of the control by chemical reaction in which [Q+X] formation of the product. is at a steady-state concentration. Below 500rpm the requirement for sufficiently Effect of Stirring Speed rapid mass transfer of the reacting anion is not met and diffusion controlled kinetics is The effect of varying stirring speed on the observed. rate of dichlorocarbene to 3-methyl-l- cyclohexene and 4-vinyl-l-cyclohexene was Hence the independence of the reaction rate studied in the range 100-800 rpm. From the constants on the stirring speed above plots of log(a-x) versus time, the pseudo- 500rpm in the present study is indicative of first order rate constants were evaluated. A extrication mechanism. The behavior is in plot of kobs against stirring speed is shown in short contrast to reactions operative through Fig. 1 (Table1). Balakrishnan et al,2005, had interfacial mechanism, where the reaction documented the kinetic studies of rate is directly proportional to the stirring dichlorocarbene addition to cyclohexene speed. using aqueous sodium hydroxide and chloroform catalyzed by polymer supported Parham, 1983, reported the continuous phase transfer catalyst, obtained an yield of increase in the rate of dichlorocarbene 213 Int.J.Curr.Microbiol.App.Sci (2014) 3(9) 211-223 addition even up to stirring speeds of Effect of catalyst amount 1200rpm. It has also been reported that the rate of an interfacial reaction is proportional The amount of catalyst was varied from to the stirring speed in the range of 600 to 0.05-0.25 mol% for the dichlorocarbene 1400rpm.The interfacial area per unit addition to 3-methyl-l-cyclohexene and 4- volume of dispersion increased linearly with vinyl-l-cyclohexene (based on the substrate increasing speed till a stage is reached where amount) and the experiments were there is no significant increase in the conducted using 15% w/w aqueous NaOH interfacial area per unit volume of dispersion solution. The pseudo first order rate with the corresponding increase in the constants are calculated from the plots of log speed. Thus increasing the stirring speed [a-x] versus time. The rate constants are changes the particle size of the dispersed dependent on the amount of catalyst used in phase.Above certain stirring speed each reaction.The increase in rate constants (500rpm), the particle size does not change. is attributed to the increase in the number of The constancy of the rate constants is active sites. Control experiments were observed not because the process is performed and no product was detected even necessarily reaction rate limited but because after 2 hours of the reaction.
Load more

Recommended publications
  • A Facile Procedure for the Generation of Dichlorocarbene from the Reaction of Carbon Tetrachloride and Magnesium Using Ultrasonic Irradiation
    Molecules 2003, 8, 608-613 molecules ISSN 1420-3049 http://www.mdpi.org A Facile Procedure for the Generation of Dichlorocarbene from the Reaction of Carbon Tetrachloride and Magnesium using Ultrasonic Irradiation Haixia Lin *, Mingfa Yang, Peigang Huang and Weiguo Cao Department of Chemistry, Shanghai University, Shanghai, 200436, P.R. China *Author to whom correspondence should be addressed: e-mail [email protected] Received: 7 April 2003; in revised form: 7 July 2003 / Accepted: 20 July 2003 / Published: 31 July 2003 Abstract: An improved method for the generation of dichlorocarbene was developed that utilizes ultrasound in the reaction of carbon tetrachloride with magnesium. High yields of gem-dichlorocyclopropane derivatives can be obtained in the presence of olefins by this method. Keywords: Dichlorocarbene; gem-dichlorocyclopropanes; ultrasonic irradiation; olefin addition; magnesium Introduction Gem-dichlorocyclopropanes are valuable intermediates in organic synthesis [1,2]. They are typically prepared by the addition of dichlorocarbene to olefins under phase-transfer catalysis conditions [3-5]. Sonochemical generation of dichlorocarbene has also been reported [6-8]. The reactions of dichlorocarbene with olefins in solid-liquid two-phase systems using ultrasonication usually afford high yields of double-bond addition products. In addition, excellent yields of diadducts have been obtained from dienes and dichlorocarbene under ultrasonication and phase-transfer catalyst [9]. Molecules 2003, 8 609 Previously, we reported a novel route for the generation of dichlorocarbene by the reaction of carbon tetrachloride with magnesium in a neutral medium and hypothesized that the mechanism of these reactions might involve a single electron transfer [10]. However, these reactions suffered from several experimental drawbacks: some of the major ones being the sudden exotherm that occurs after an unpredictable induction period, foaming, and in some cases, the use of iodine as the activating agent.
    [Show full text]
  • Chloroform 18.08.2020.Pdf
    Chloroform Chloroform, or trichloromethane, is an organic compound with formula CHCl3. It is a colorless, sweet-smelling, dense liquid that is produced on a large scale as a precursor to PTFE. It is also a precursor to various refrigerants. It is one of the four chloromethanes and a trihalomethane. It is a powerful anesthetic, euphoriant, anxiolytic and sedative when inhaled or ingested. Formula: CHCl₃ IUPAC ID: Trichloromethane Molar mass: 119.38 g/mol Boiling point: 61.2 °C Density: 1.49 g/cm³ Melting point: -63.5 °C The molecule adopts a tetrahedral molecular geometry with C3v symmetry. Chloroform volatilizes readily from soil and surface water and undergoes degradation in air to produce phosgene, dichloromethane, formyl chloride, carbon monoxide, carbon dioxide, and hydrogen chloride. Its half-life in air ranges from 55 to 620 days. Biodegradation in water and soil is slow. Chloroform does not significantly bioaccumulate in aquatic organisms. Production:- In industry production, chloroform is produced by heating a mixture of chlorine and either chloromethane (CH3Cl) or methane (CH4). At 400–500 °C, a free radical halogenation occurs, converting these precursors to progressively more chlorinated compounds: CH4 + Cl2 → CH3Cl + HCl CH3Cl + Cl2 → CH2Cl2 + HCl CH2Cl2 + Cl2 → CHCl3 + HCl Chloroform undergoes further chlorination to yield carbon tetrachloride (CCl4): CHCl3 + Cl2 → CCl4 + HCl The output of this process is a mixture of the four chloromethanes (chloromethane, dichloromethane, chloroform, and carbon tetrachloride), which can then be separated by distillation. Chloroform may also be produced on a small scale via the haloform reaction between acetone and sodium hypochlorite: 3 NaClO + (CH3)2CO → CHCl3 + 2 NaOH + CH3COONa Deuterochloroform[ Deuterated chloroform is an isotopologue of chloroform with a single deuterium atom.
    [Show full text]
  • Gas-Solid Alkali Destruction of Volatile Chlorocarbons
    LA-13042-MS Gas-Solid Alkali Destruction of Volatile Chlorocarbons c£lVi •% to BO Los Alamos NATIONAL LABORATORY Los Alamos National Laboratory is operated by the University of California for the United States Department of Energy under contract W-7405-ENG-36- An Affirmative Action/Equal Opportunity Employer This report was prepared as an account of work sponsored by an agency of the United States Government. Neither The Regents of the University of California, the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by The Regents of the University of California, the United States Government, or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of The Regents of the University of California, the United States Government, or any agency thereof. The Los Alamos National Laboratory strongly supports academic freedom and a researcher's right to publish; therefore, the Laboratory as an institution does not endorse the viewpoint of a publication or guarantee its technical correctness. DISCLAIMER Portions of this document may be illegible in electronic image products. Images are produced from the best aTaiiable original document. LA-13042-MS UC-901 Issued: December 1995 Gas-Solid Alkali Destruction of Volatile Chlorocarbons Jerry Foropoulos, Jr.
    [Show full text]
  • Lecture 13 Electrophilic Aromatic Substitution I 5.1 Principles
    NPTEL – Chemistry – Principles of Organic Synthesis Lecture 13 Electrophilic Aromatic Substitution I 5.1 Principles The reaction occurs in two stages: the electrophile adds to one carbon atom of the aromatic ring, yielding a carbocation in which the positive charge is delocalized, and a proton is then eliminated from the adduct. H E H E H E E -H E 5.2 Formation of Carbon-Carbon Bonds 5.2.1 Friedel-Crafts Acylation Acylation of aromatic rings is generally peroformed using acid chloride or acid anhydride as an acylating agent in the presence of Lewis acid. O Z RCOCl, AlCl Z 3 R H2O Mechanism AlCl3 RCOCl RC=O + AlCl4 H H RC=O COR Z Z COR Z Joint initiative of IITs and IISc – Funded by MHRD Page 1 of 26 NPTEL – Chemistry – Principles of Organic Synthesis In some circumstances, carboxylic acid is used as an acylating agent in the presence of a proton acid. HO OH O 2 PhOH, H2SO4 O O -H2O O O Phenolphthalein Indicator Intramolecular reactions are of particular value to construct cyclic systems. These reactions are usually carried out using dibasic acid anhydrides. For example, the synthesis -tetralone has been accomplished from benzene and succinic anhydride using AlCl3 in 80% yield. O O OH OH AlCl3 reduction + O O O O SOCl2 Cl AlCl3 O O Joint initiative of IITs and IISc – Funded by MHRD Page 2 of 26 NPTEL – Chemistry – Principles of Organic Synthesis Examples: 5 mol% Tb(OTf)3 CO H 2 PhCl O D.-M. Cui, C. Zhang, M. Kawamura, S.
    [Show full text]
  • Carbene Rearrangements: Intramolecular Interaction of a Triple Bond with a Carbene Center
    An Abstract OF THE THESIS OF Jose C. Danino for the degree of Doctor of Philosophy in Chemistry presented on _Dcc, Title: Carbene RearrangementE) Intramolecular Interaction of a Triple Bond with aCarbene Center Redacted for Privacy Abstract approved: Dr. Vetere. Freeman The tosylhydrazones of2-heptanone, 4,4-dimethy1-2- heptanone, 6-heptyn-2-one and 4,4-dimethy1-6-heptyn-2- one were synthesizedand decomposed under a varietyof reaction conditions:' drylithium and sodium salt pyrolyses, sodium methoxide thermolysesin diglyme and photolyses of the lithium salt intetrahydrofuran. The saturated ana- logues 2-heptanone tosylhydrazoneand its 4,4-dimethyl isomer afforded the alkenesarising from 6-hydrogeninser- product distribution in the tion. It was determined that differ- dry salt pyrolyses of2-heptanone tosylhydrazone was ent for the lithiumand the sodium salts. However, the product distribution of thedry sodium salt was verysimilar diglyme to product distributionobtained on thermolysis in explained by a with sodium methoxide. This difference was reaction of lithium bromide(present as an impurity inall compound to the lithium salts)with the intermediate diazo afford an organolithiumintermediate that behaves in a some- what different fashionthan the free carbene.The unsaturated analogues were found to produce a cyclic product in addition to the expected acyclic alkenes arising from 3-hydrogen insertion. By comparison of the acyclic alkene distri- bution obtained in the saturated analogues with those in the unsaturated analogues, it was concluded that at leastsome cyclization was occurring via addition of the diazo moiety to the triple bond. It was determined that the organo- lithium intermediateresulting from lithium bromide cat- alyzed decomposition of the diazo compound was incapable of cyclization.
    [Show full text]
  • Interfacial Processes—The Key Steps of Phase Transfer Catalyzed
    Review Interfacialcatalysts Processes—The Key Steps of Phase Transfer Catalyzed Reactions Review InterfacialMieczysław Mąkosza Processes—The 1,* and Michał Fedoryński 2 Key Steps of Phase Transfer1 Institute of Organic Catalyzed Chemistry, Polish Reactions Academy of Sciences, Kasprzaka 44/52, 01‐224 Warsaw, Poland 2 Faculty of Chemistry, Warsaw University of Technology, Noakowskiego 3, 00‐664 Warsaw, Poland; Mieczysł[email protected] M ˛akosza 1,* and Michał Fedory ´nski 2 * Correspondence: [email protected]; Tel: +48‐22‐3432334 1 Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland 2Received:Faculty 18 of November Chemistry, 2020; Warsaw Accepted: University 5 December of Technology, 2020; Published: Noakowskiego 8 December 3, 00-664 2020 Warsaw, Poland; [email protected] *Abstract:Correspondence: After short [email protected]; historical introduction, Tel.: + interfacial48-22-3432334 mechanism of phase transfer catalyzed (PTC) reactions of organic anions, induced by aqueous NaOH or KOH in two‐phase systems is Received:formulated. 18 NovemberSubsequently 2020; experimental Accepted: 5 December evidence 2020; that Published: supports 8 the December interfacial 2020 deprotonation as the key initial step of these reactions is presented. Abstract: After short historical introduction, interfacial mechanism of phase transfer catalyzed (PTC) reactionsKeywords: of organiccarbanions; anions, dichlorocarbene; induced by aqueous sodium NaOH hydroxide; or KOH ininterfacial two-phase processes;
    [Show full text]
  • Review Article Synthesis and Reactions of Five-Membered Heterocycles Using Phase Transfer Catalyst (PTC) Techniques
    Hindawi Publishing Corporation Journal of Chemistry Volume 2014, Article ID 163074, 47 pages http://dx.doi.org/10.1155/2014/163074 Review Article Synthesis and Reactions of Five-Membered Heterocycles Using Phase Transfer Catalyst (PTC) Techniques Ahmed M. El-Sayed,1 Omyma A. Abd Allah,1 Ahmed M. M. El-Saghier,1 and Shaaban K. Mohamed2,3 1 Department of Chemistry, Faculty of Science, Sohag University, Sohag 82524, Egypt 2 Chemistry and Environmental Division, Manchester Metropolitan University, Manchester M1 5GD, UK 3 Chemistry Department, Faculty of Science, Minia University, El-Minia 61519, Egypt Correspondence should be addressed to Omyma A. Abd Allah; [email protected] Received 1 May 2013; Revised 15 September 2013; Accepted 28 October 2013; Published 25 February 2014 Academic Editor: Jorge F. Fernandez-Sanchez Copyright © 2014 Ahmed M. El-Sayed et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Phase transfer catalysts (PTCs) have been widely used for the synthesis of organic compounds particularly in both liquid-liquid and solid-liquid heterogeneous reaction mixtures. They are known to accelerate reaction rates by facilitating formation of interphase transfer of species and making reactions between reagents in two immiscible phases possible. Application of PTC instead of traditional technologies for industrial processes of organic synthesis provides substantial benefits for the environment. On the basis of numerous reports it is evident that phase-transfer catalysis is the most efficient way for generation and reactions of many active intermediates.
    [Show full text]
  • STUDIES of CARBENE-SOLVENT INTERACTIONS DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor
    STUDIES OF CARBENE-SOLVENT INTERACTIONS DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Eric M. Tippmann, B.S. ***** The Ohio State University 2003 Dissertation Committee: Approved by Professor Matthew S. Platz, Adviser Professor Terry L. Gustafson Professor Christopher M. Hadad Adviser Department of Chemistry ABSTRACT Several new tricyclic-carbene precursors have been synthesized. Photolysis (266, 300, or 308 nm) of these precursors generates free carbenes in solution. This was demonstrated through trapping studies performed with pyridine and tetramethylethylene. The new carbenes (chlorofluoro-, fluorocarbomethoxy-, chloro- and fluoroamidecarbenes) were fully characterized by laser flash photolysis techniques using time-resolved infrared and UV-Vis spectroscopy. The new carbenes, along with several other known carbenes, were utilized in the study of carbene-solvent interactions. One class of carbenes, the haloamide carbenes, demonstrated significant solvent-dependent chemistry. Both time resolved infrared and UV-Vis spectroscopy generated results indicative of significant carbene-solvent interactions. Generally, ethereal solvents were able to retard the bimolecular reactivity of chloro- and fluoroamidecarbenes with carbene traps. The lifetime of the carbene was also dramatically extended in some cases. Time- resolved infrared spectroscopy was able to directly observe the chloroamide carbene solvated by small amounts of dioxane in Freon-113. Other potentially ligating solvents, such as benzene and acetonitrile for example, did not demonstrate similar reactivity. Density Functional and MP2 theoretical calculations were performed to assist in assigning reactive intermediates as well as determining reaction barriers. ii To Sohie iii ACKNOWLEDGMENTS I thank my adviser for supplying a lifetime's worth of example to follow, both personally and professionally.
    [Show full text]
  • Synthesis and Photochemistry of New Carbene Precursors
    SYNTHESIS AND PHOTOCHEMISTRY OF NEW CARBENE PRECURSORS A Senior Honors Thesis Presented in Partial Fulfillment of the Requirements for graduation with distinction in Chemistry in the undergraduate colleges of The Ohio State University By Christopher M. Cassara ***** The Ohio State University June 2005 Project Advisor: Professor Matthew S. Platz, Department of Chemistry ABSTRACT Carbenes are neutral divalent reactive intermediates containing a carbon atom surrounded by only six valence electrons. Because of this electron deficiency, carbenes are very short-lived intermediates and react with a variety of functional groups. One of the most commonly used applications of carbenes is in cyclopropane synthesis. This research has focused on the synthesis of new, novel carbene precursors and the study of their photochemistry. The purpose of this research is twofold: 1) to trap the carbene with pyridine and characterize the UV spectra of the carbene ylide intermediate and 2) to determine the lifetimes and reaction rates of carbenes with various reagents. The lifetime of the carbene and the rate of its reaction with alkenes will be used to form a better understanding of the relationship between carbene structure and reactivity. Laser Flash Photolysis (LFP) techniques were used to generate the carbene, which subsequently reacted with pyridine to form an ylide. This reaction was necessary because we were not able to detect the carbene directly. The carbenes being studied cannot be directly detected because they do not exhibit a UV chromophore at or above 300 nm. Trapping the carbene with pyridine yields a species with a strong UV absorbtion at 480 nm, which is easily detected.
    [Show full text]
  • Pyridine: a New Arrival in the Heterocalixarene Family
    Calix[4]pyridine: a new arrival in the heterocalixarene family Vladim´ır Kr´al,a,b Philip A. Gale,a Pavel Anzenbacher Jr.,a,b Karolina Jurs´ıkov´a,a Vincent Lyncha and Jonathan L. Sessler*a a Department of Chemistry and Biochemistry, The University of Texas at Austin, Austin, Texas, 78712-1167, USA b Institute of Chemical Technology, Department of Analytical Chemistry, Prague, 166 28 Czech Republic Reaction of dichlorocarbene with meso-octamethyl- hydrogen bonds may influence the conformation of the calix[4]pyrrole causes pyrrole ring expansion, producing macrocycle. chlorocalixpyridinopyrroles and chlorocalixpyridines. Crystals of the calix[3]pyridino[1]pyrrole were grown from a MeOH–CH2Cl2–hexanes solvent mixture.§ As in the structure Considerable effort of late has been devoted to synthesizing new macrocycles containing pyridine subunits. While many Cl such systems have been reported, some of considerable elegance,1 one of the simplest conceivable pyridine-containing N N macrocycles, calix[4]pyridine, remains unknown. H :CCl2 –HCl Currently, close analogues of calix[4]pyridine, in the form of NH HN NH HN homocalixpyridines2 and tetrapyridine tetraone3 macrocycles H H are known. However, macrocyclic systems with pyridine rings N N linked in the 2 and 6 positions via a single sp3 hybridized carbon atom have yet to be prepared. We have now discovered a 52:CCl2 general synthetic strategy that not only allows for the prepara- –HCl tion of calix[4]pyridine derivatives (e.g. 1), but also provides Cla Clb Cla Clb access to calix[n]pyridino[n]pyrroles (m + n = 4). While some species related to this latter set of macrocycles are known, N N Cla namely mixed porphyrin-like pyrrole-pyridine systems and calixpyridinopyrroles containing one or two pyridines,4 NHHN or NH N calix[3]pyridine[1]pyrrole derivatives (e.g.
    [Show full text]
  • Enhanced Mixing of Biphasic Liquid-Liquid Systems for the Synthesis of Gem-Dihalocyclopropanes Using Packed Bed Reactors
    Journal of Flow Chemistry (2019) 9:27–34 https://doi.org/10.1007/s41981-018-0026-1 COMMUNICATIONS Enhanced mixing of biphasic liquid-liquid systems for the synthesis of gem-dihalocyclopropanes using packed bed reactors Timo von Keutz1,2 & David Cantillo1,2 & C. Oliver Kappe1,2 Received: 14 November 2018 /Accepted: 7 December 2018 /Published online: 7 January 2019 # The Author(s) 2019 Abstract A continuous flow procedure for the gem-dichlorocyclopropanation of alkenes has been developed. The method is based on the generation of dichlorocarbene utilizing the classical biphasic aqueous sodium hydroxide/chloroform system. This reaction typically requires vigorous stirring for several hours in batch for completion. Tarry materials precipitate due to partial polymer- ization of dichlorocarbene and the process is difficult to scale. To overcome these problems and achieve very efficient mixing during the flow process a column reactor packed with PTFE beads as inert filling material has been used. PTFE beads have been found to be the optimal material to obtain fine dispersions of the aqueous phase in the organic solution. By heating the packed- bed reactor at 80 °C excellent conversions have been achieved after a residence time of only 4 min. The process has been applied for the synthesis of Ciprofibrate, a dichlorocyclopropane-containing drug used as treatment for several diseases associated with high lipid content in blood. Keywords Dichlorocarbene . Phase-transfer catalysis . Packed-bed reactor . gem-dichlorocyclopropanation . Ciprofibrate . Continuous flow Introduction transfer, which in turn depends on the surface contact area between the two phases [5, 6]. In batch reactors highly Biphasic liquid-liquid systems are very important in pro- dispersed biphasic liquid-liquid mixtures can only be ob- cess chemistry and the pharmaceutical industry.
    [Show full text]
  • New Polymer-Supported Multi-Site Phase Transfer Catalyst in Dichlorocarbene Addition to Styrene P
    International Journal of Scientific Research and Modern Education (IJSRME) ISSN (Online): 2455 – 5630 & Impact Factor: 3.110 National Conference on Recent Trends in Applied Chemistry (NCRTAC–2016) Easwari Engineering College, Ramapuram, Chennai, Tamilnadu NEW POLYMER-SUPPORTED MULTI-SITE PHASE TRANSFER CATALYST IN DICHLOROCARBENE ADDITION TO STYRENE P. Gopinath* & E. Murugan** * Department of Chemistry, Alpha College of Engineering, Udayavar Koil Street, Thirumazhisai, Poonamalle, Chennai, Tamilnadu ** Department of Physical Chemistry, School of Chemical Sciences University of Madras, Guindy Campus, Chennai, Tamilnadu Abstract: A new insoluble polymer-supported multi-site phase transfer catalyst containing two active sites was synthesized by simplified procedure. This di-site polymer-supported PTC was characterized by FT-IR, 13C NMR, TGA, chloride ion & SEM analyses. Similarly, polymer-supported single-site catalyst was also prepared with the same catalytic moiety. The catalytic efficiency was ascertained through dichlorocarbene addition to styrene under pseudo-first order reaction conditions. The rate constants were calculated by following the disappearance of styrene through Gas Chromatography. It was found that the di-site PS-PTC was more effective than single-site PS-PTC in terms of rate constant. The kinetic variables such as stirring speed, [substrate], [NaOH], [catalyst], and temperature were thoroughly studied. The thermodynamic parameters viz., activation energy, enthalpy, entropy and free energy change were also calculated. Based on the observed kinetic and thermodynamic results, an interfacial mechanism was proposed. Key Words: Multisite, Dichorocarbene, Styrene & Interfacial Mechanism 1. Introduction: Generally the reactions between two immiscible substrates are difficult to carry out because they do not contact each other. Phase transfer catalysis (PTC) is a well- known technique to carry out these types of reactions at high rate.
    [Show full text]