DOCSLIB.ORG

Protonation and Other Acid-Base Chemistry Of

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Protonation and Other Acid-Base Chemistry Of PROTONATION AND OTHER ACID-BASE CHEMISTRY OF CHLOROPHOSPHAZENES A Thesis Presented to The Graduate Faculty of the University of Akron In Partial Fulfillment of the Requirements For Degree Master of Chemistry Bang Hoang August, 2005 PROTONATION AND OTHER ACID-BASE CHEMISTRY OF CHLOROPHOSPHAZENES Bang Hoang Thesis Approved: Accepted _______________________________ _____________________________ Advisor Dean of the College Dr. Claire Tessier Dr. Charles Monroe _______________________________ _____________________________ Faculty Reader Dean of the Graduate School Dr. Wiley Youngs Dr. George Newkome _______________________________ _____________________________ Department Chair Date Dr. David Perry ii DEDICATION This is dedicated to my parents, Be and Cam Hoang, for their tireless, hard work and sacrifice that made everything possible. And to Audry for her strength and faith. iii ACKNOWLEDGEMENTS A very special thanks goes Dr. Claire Tessier for her guidance, knowledge and friendship. Her sincerity and wisdom will never be forgotten. Also a heartfelt thanks must go to Amy Heston and Tatianna Eliseeva for the countless times they have aided me in the lab. Thank you to Dr. Wiley Youngs and his group for their help through the years. Finally, thanks to Alyison Leigh for her assistance with mass spectra. iv TABLE OF CONTENTS page Table of Figures ……………………………………………………………………….. vi CHAPTER I. INTRODUCTION …………………………………………………………….. 1 II. EXPERIMENTAL ...…………………………………………………………... 11 III. RESULTS AND DISCUSSION ...………...………………………………….. 15 IV. CONCLUSION ...……………………………………………………………... 29 REFERENCES ...…………...…..…………………………………………………….... 31 v LIST OF FIGURES Figure page 1. Phosphazene Trimer and Linear Phosphazene …………………………..… 1 2. Allcock Mechanism. ……………………………………..…………………….. 4 3. Sulkowski Mechanism3 …………………………………….…………………. 6 31 4. P NMR Spectrum of [PCl2N]n Obtained n the Synthesis of (PCl2N)3 Magnified …...………………………....…………….. 16 313 5. P NMR Spectrum of the [PCl2N]n Obtained n the Synthesis of (PCl2N)3 …………………………………..………..…………… 17 6. Mass Spectrum of [PCl2N]n in DCTB ……………………………..………... 19 7. Mass Spectrum of [PCl2N]n in DCTB with NaTFA …………………...…... 20 8. Mass Spectrum of [PCl2N]n in DCTB with LiTFA ………………………… 21 9 1H NMR Spectrum of Magic Acid in Benzene ……………………..……… 22 1 10. H NMR Spectrum of (PCl2N)3 and Magic Acid …………………..........… 23 31 11. P NMR Spectrum of [PCl2N]3 and Magic Acid ………………………..… 24 31 12. P NMR Spectrum of PCl2N]3 and Magic Acid Magnified …...…............. 24 1 13. H NMR Spectrum of Commercial [PCl2N]n with HOTf ………...…......... 25 31 14. P Spectrum of [PNCl2]n and HOTf …….…..………………….…………... 27 vi CHAPTER 1 INTRODUCTION The term “phosphazene” is used to encompass a class of compounds that contain one or more subunits of “-P=N-” in their structures. These compounds can vary greatly in size from several atoms to large polymers. In the polymers, nitrogen and phosphorus atoms alternate to make up the backbone with single and double bonds between them also alternating. The examples given below (Figure 1) are a phosphazene trimer, (NPR2)3, and linear polyphosphazene, [NPCl2]n. On the phosphorus atom, there are two substituents often represented by symbol “R”. R can be an amine, alcohol, akyl or aryl groups or a halogen in the inorganic polymer. RR P R N N RR PN P P R N R R n Figure 1. Phosphazene Trimer and Linear Phosphazene 1 In the 1890's, H. N. Stokes was studying compounds that formed when phosphorus pentachloride reacted with ammonia.1 He was the first to put forth the possible structure (NPCl2)3 and also other homologues. Further he accounted how, when heated, these compounds would form an “inorganic rubber.” In a time before even the concept of polymers was commonly accepted, Stokes had suggested that this rubber was in fact a polymer. Four decades later in 1936, X- ray diffraction studies performed by Meyer, Lotmar and Pankow confirmed Stokes' belief. In 1948, Goldschmidt and Dishon attempted to use organic molecules to replace the chlorine atoms in the rubber but were unsuccessful. The area of phosphazene research sat largely dormant until the mid 1960's when Allcock, Kugul and Valan published a series of papers on the subject. They described how the inorganic rubber's P-Cl bond was hydrolytically unstable. The unstable inorganic polymer could be used as a precursor for a number of interesting substituted polymers. Additionally they showed that the [PCl2N]n polymer could be dissolved in a number of solvents such as benzene, toluene, cyclohexane and tetrahydrofuran. Insoluble rubbers, they said, were crosslinked. These papers inspired great interest and research. That curiosity still lives. Phosphazenes hold great promise as a class of compounds due to their very interesting properties and potential uses. Linear polymers have great flexibility over a wide range of temperatures and are chemically stable to acid, bases and other reactive chemicals.1 These traits make them ideal for uses such 2 as O-rings and gaskets. The polymer is also heat resistant and flame retardant and could be used in fire-resistant materials such as textiles. Cyclic oligomers 2 have been suggested for use in antitumor drugs, insect control and fertilizer. Polydichlorophosphazene [PCl2N]n is the precursor for many phosphazene compounds. The most common synthesis involves the melt 1 polymerization of (PCl2N)3. This ring opening polymerization (ROP) is performed by heating the trimer to 250° C for about 8 hours. Longer reaction time and higher temperature can lead to cross-linking the polymer. The crosslinked polymer is generally considered an undesirable side product. It has been show that the reaction is catalyzed the presence of a Lewis acid such as BCl3 or AlCl3. Also it appears that water in trace amounts is needed to catalyze the reaction.3 This is evidenced by the readily proceeding polymerization in glass reaction flasks but not in dried quartz phials. Glass walls are known to hold onto water in minute amounts even when thoroughly dried. However in quartz vials, water can be driven off much more thoroughly. The inability to polymerize in quartz is believed to be caused by this lack of trace moisture. Although the ring opening polymerization has been long known, the mechanism by which the polymerization occurs is still up to speculation. One mechanism is suggested by Allcock and Best (Figure 2).1 Noting that the presence of a Lewis acid promotes ROP, they propose that a Cl- anion first disassociates from the trimer. This leaves phosphorus with a positive formal 3 Cl- Cl Cl Cl Cl Cl P P P N N N N Cl Cl N N Cl Cl Cl Cl P P P P P P N N Cl N Cl Cl Cl Cl Cl Cl Cl Cl Cl P N PNP Cl Cl N Cl Cl NP P N N Cl Cl Cl n P P N Cl Cl Figure 2. Allcock Mechanism1 charge. The phosphorus can then be attacked by a nitrogen atom from another ring. The attack forms a bond between the phosphorus and attacking nitrogen. Also it opens the ring of the attacking nitrogen. The phosphorus atom that used to be next to the attacking nitrogen is then left with a positive charge. This phosphorus atom serves as a site available for the continuation of the polymerization. Disassociation of the Cl- ion in the melt is supported by conductivity studies and the catalyzing nature of the presence of Lewis acids. Further, polymerization is inhibited by the substitution of chlorine with organic groups that are less likely to disassociate. An intriguing examination of the initial stages of polymerization based on mass spectrometric studies was reported by Traldi.4 This report is quite novel because mass spectroscopy is usually used to obtain structural data. 4 Traditionally, examination of the mass to charge ratios (m/z) of mass spectra leads to the masses of the compound and its fragments. By analysis of the masses of the fragments, structural data about the analyte can be gained. For instance, the mass spectra of a polymer will often contain a series of regularly- repeating m/z’s. The difference between these peaks represents the mass of the repeat unit of the polymer. In this particular report,4 Traldi noted that when the mass spectra of (PCl2N)3 (m.w. 345) was obtained using electron ionization techniques (EI), the m/z of 310 was prominent, a difference of 35 from the trimers molecular weight. This corresponds to the loss of Cl-. Recognizing this as the initial step of the Allcock’s proposed mechanism, Traldi attempted to induce polymerization inside the ionization chamber. He switched from EI to chemical ionization (CI). This had the effect of raising the pressure inside the chamber to 1 torr. He also increased the temperature of the chamber to 200°C. When the mass spectra were then obtained, m/z’s corresponding to the masses of [PCl2N]n with 4 ≤ n ≤ 21 were observed. Demonstration that ionization causes the loss of Cl- from the trimer and then that polymerization can occur in the ionization chamber lends credence to Allcock’s mechanism. Sulkowski suggests an alternative mechanism to Allcock’s.3 In Sulkowski’s mechanism (Figure 3), a nitrogen atom on the chain is protonated to form a linear azophosphonium cation. He suggests that the proton source could be from trace amounts of water left on the walls of the reaction vessel. The water 5 Cl Cl Cl Cl Cl Cl P P H P N N NH H+ Cl Cl Cl P P P N Cl N Cl N Cl Cl Cl N p NP N3P3Cl6 P Cl N N - HCl Cl Cl P P N Cl Cl Figure 3. Sulkowski Mechanism3 hydrolyzes the P-Cl bonds to give small amounts of HCl. This protonation could lead the P-N bond scission and make phosphorus available for nucleophilic attack. The nitrogen from a trimer could attack and create a larger phosphonium cation. One interesting aspect of Sulkowski’s proposed mechanism is the protonation of the nitrogen on the trimer.
Load more

Recommended publications
  • Synergistic Effect of Acids and HFIP on Friedel-Crafts Reactions of Alcohols and Cyclopropanes Vuk Vukovic
    Synergistic effect of acids and HFIP on Friedel-Crafts reactions of alcohols and cyclopropanes Vuk Vukovic To cite this version: Vuk Vukovic. Synergistic effect of acids and HFIP on Friedel-Crafts reactions of alcohols andcy- clopropanes. Organic chemistry. Université de Strasbourg, 2018. English. NNT : 2018STRAF068. tel-02918037 HAL Id: tel-02918037 https://tel.archives-ouvertes.fr/tel-02918037 Submitted on 20 Aug 2020 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. UNIVERSITÉ DE STRASBOURG ÉCOLE DOCTORALE DES SCIENCES CHIMIQUES (ED 222) Laboratoire de Catalyse Chimique Institut de Science et d'Ingénierie Supramoléculaires (UMR 7006) THÈSE de DOCTORAT présentée par Vuk VUKOVIĆ soutenue le 14 décembre 2018 pour obtenir le grade de : Docteur de l’Université de Strasbourg Discipline/ Spécialité : Chimie organique Synergistic Effect of Acids and HFIP on Friedel-Crafts Reactions of Alcohols and Cyclopropanes THESE dirigée par : Prof. MORAN Joseph Université de Strasbourg RAPPORTEURS : Prof. THIBAUDEAU Sébastien Université de Poitiers Prof. GANDON Vincent Université Paris-Sud 11 EXAMINATEUR: Dr WENCEL-DELORD Joanna Université de Strasbourg Synergistic Effect of Acids and HFIP on Friedel-Crafts Reactions of Alcohols and Cyclopropanes Table of Contents page Table of Contents I Acknowledgement and Dedication V List of Abbreviations XIII Résumé XVII Chapter 1.
    [Show full text]
  • Is There an Acid Strong Enough to Dissolve Glass? – Superacids
    ARTICLE Is there an acid strong enough to dissolve glass? – Superacids For anybody who watched cartoons growing up, the word unit is based on how acids behave in water, however as acid probably springs to mind images of gaping holes being very strong acids react extremely violently in water this burnt into the floor by a spill, and liquid that would dissolve scale cannot be used for the pure ‘common’ acids (nitric, anything you drop into it. The reality of the acids you hydrochloric and sulphuric) or anything stronger than them. encounter in schools, and most undergrad university Instead, a different unit, the Hammett acidity function (H0), courses is somewhat underwhelming – sure they will react is often preferred when discussing superacids. with chemicals, but, if handled safely, where’s the drama? A superacid can be defined as any compound with an People don’t realise that these extraordinarily strong acids acidity greater than 100% pure sulphuric acid, which has a do exist, they’re just rarely seen outside of research labs Hammett acidity function (H0) of −12 [1]. Modern definitions due to their extreme potency. These acids are capable of define a superacid as a medium in which the chemical dissolving almost anything – wax, rocks, metals (even potential of protons is higher than it is in pure sulphuric acid platinum), and yes, even glass. [2]. Considering that pure sulphuric acid is highly corrosive, you can be certain that anything more acidic than that is What are Superacids? going to be powerful. What are superacids? Its all in the name – super acids are intensely strong acids.
    [Show full text]
  • The Strongest Acid Christopher A
    Chemistry in New Zealand October 2011 The Strongest Acid Christopher A. Reed Department of Chemistry, University of California, Riverside, California 92521, USA Article (e-mail: [email protected]) About the Author Chris Reed was born a kiwi to English parents in Auckland in 1947. He attended Dilworth School from 1956 to 1964 where his interest in chemistry was un- doubtedly stimulated by being entrusted with a key to the high school chemical stockroom. Nighttime experiments with white phosphorus led to the Headmaster administering six of the best. He obtained his BSc (1967), MSc (1st Class Hons., 1968) and PhD (1971) from The University of Auckland, doing thesis research on iridium organotransition metal chemistry with Professor Warren R. Roper FRS. This was followed by two years of postdoctoral study at Stanford Univer- sity with Professor James P. Collman working on picket fence porphyrin models for haemoglobin. In 1973 he joined the faculty of the University of Southern California, becoming Professor in 1979. After 25 years at USC, he moved to his present position of Distinguished Professor of Chemistry at UC-Riverside to build the Centre for s and p Block Chemistry. His present research interests focus on weakly coordinating anions, weakly coordinated ligands, acids, si- lylium ion chemistry, cationic catalysis and reactive cations across the periodic table. His earlier work included extensive studies in metalloporphyrin chemistry, models for dioxygen-binding copper proteins, spin-spin coupling phenomena including paramagnetic metal to ligand radical coupling, a Magnetochemi- cal alternative to the Spectrochemical Series, fullerene redox chemistry, fullerene-porphyrin supramolecular chemistry and metal-organic framework solids (MOFs).
    [Show full text]
  • WO 2015/014733 Al 5 February 2015 (05.02.2015) P O P C T
    (12) INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT) (19) World Intellectual Property Organization I International Bureau (10) International Publication Number (43) International Publication Date WO 2015/014733 Al 5 February 2015 (05.02.2015) P O P C T (51) International Patent Classification: (81) Designated States (unless otherwise indicated, for every C07D 233/64 (2006.01) C07D 403/06 (2006.01) kind of national protection available): AE, AG, AL, AM, A 43/40 (2006.01) C07D 239/26 (2006.01) AO, AT, AU, AZ, BA, BB, BG, BH, BN, BR, BW, BY, A 43/50 (2006.01) C07D 417/06 (2006.01) BZ, CA, CH, CL, CN, CO, CR, CU, CZ, DE, DK, DM, A0 43/54 (2006.01) C07D 249/08' (2006.01) DO, DZ, EC, EE, EG, ES, FI, GB, GD, GE, GH, GM, GT, A0 43/653 (2006.01) C07D 213/57 (2006.01) HN, HR, HU, ID, IL, IN, IR, IS, JP, KE, KG, KN, KP, KR, C07D 401/06 (2006.01) KZ, LA, LC, LK, LR, LS, LT, LU, LY, MA, MD, ME, MG, MK, MN, MW, MX, MY, MZ, NA, NG, NI, NO, NZ, (21) International Application Number: OM, PA, PE, PG, PH, PL, PT, QA, RO, RS, RU, RW, SA, PCT/EP2014/065994 SC, SD, SE, SG, SK, SL, SM, ST, SV, SY, TH, TJ, TM, (22) International Filing Date: TN, TR, TT, TZ, UA, UG, US, UZ, VC, VN, ZA, ZM, 25 July 2014 (25.07.2014) ZW. (25) Filing Language: English (84) Designated States (unless otherwise indicated, for every kind of regional protection available): ARIPO (BW, GH, (26) Publication Language: English GM, KE, LR, LS, MW, MZ, NA, RW, SD, SL, SZ, TZ, (30) Priority Data: UG, ZM, ZW), Eurasian (AM, AZ, BY, KG, KZ, RU, TJ, 2256/DEL/2013 29 July 2013 (29.07.2013) IN TM), European (AL, AT, BE, BG, CH, CY, CZ, DE, DK, EE, ES, FI, FR, GB, GR, HR, HU, IE, IS, IT, LT, LU, LV, (71) Applicant: SYNGENTA PARTICIPATIONS AG MC, MK, MT, NL, NO, PL, PT, RO, RS, SE, SI, SK, SM, [CH/CH]; Schwarzwaldallee 215, CH-4058 Basel (CH).
    [Show full text]
  • Amide Activation: an Emerging Tool for Chemoselective Synthesis
    Featuring work from the research group of Professor As featured in: Nuno Maulide, University of Vienna, Vienna, Austria Amide activation: an emerging tool for chemoselective synthesis Let them stand out of the crowd – Amide activation enables the chemoselective modification of a large variety of molecules while leaving many other functional groups untouched, making it attractive for the synthesis of sophisticated targets. This issue features a review on this emerging field and its application in total synthesis. See Nuno Maulide et al., Chem. Soc. Rev., 2018, 47, 7899. rsc.li/chem-soc-rev Registered charity number: 207890 Chem Soc Rev View Article Online REVIEW ARTICLE View Journal | View Issue Amide activation: an emerging tool for chemoselective synthesis Cite this: Chem. Soc. Rev., 2018, 47,7899 Daniel Kaiser, Adriano Bauer, Miran Lemmerer and Nuno Maulide * It is textbook knowledge that carboxamides benefit from increased stabilisation of the electrophilic carbonyl carbon when compared to other carbonyl and carboxyl derivatives. This results in a considerably reduced reactivity towards nucleophiles. Accordingly, a perception has been developed of amides as significantly less useful functional handles than their ester and acid chloride counterparts. Received 27th April 2018 However, a significant body of research on the selective activation of amides to achieve powerful DOI: 10.1039/c8cs00335a transformations under mild conditions has emerged over the past decades. This review article aims at placing electrophilic amide activation in both a historical context and in that of natural product rsc.li/chem-soc-rev synthesis, highlighting the synthetic applications and the potential of this approach. Creative Commons Attribution 3.0 Unported Licence.
    [Show full text]
  • Superacid Chemistry
    SUPERACID CHEMISTRY SECOND EDITION George A. Olah G. K. Surya Prakash Arpad Molnar Jean Sommer SUPERACID CHEMISTRY SUPERACID CHEMISTRY SECOND EDITION George A. Olah G. K. Surya Prakash Arpad Molnar Jean Sommer Copyright # 2009 by John Wiley & Sons, Inc. All rights reserved Published by John Wiley & Sons, Inc., Hoboken, New Jersey Published simultaneously in Canada No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning, or otherwise, except as permitted under Section 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, (978) 750-8400, fax (978) 750-4470, or on the web at www.copyright.com. Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, (201) 748-6011, fax (201) 748-6008, or online at http://www.wiley.com/go/permission. Limit of Liability/Disclaimer of Warranty: While the publisher and author have used their best efforts in preparing this book, they make no representations or warranties with respect to the accuracy or completeness of the contents of this book and specifically disclaim any implied warranties of merchantability or fitness for a particular purpose. No warranty may be created or extended by sales representatives or written sales materials. The advice and strategies contained herein may not be suitable for your situation.
    [Show full text]
  • Reactivity Landscape of Pyruvate Under Simulated Hydrothermal Vent
    Reactivity landscape of pyruvate under simulated SEE COMMENTARY hydrothermal vent conditions Yehor Novikova and Shelley D. Copleyb,c,1 aDepartment of Chemistry and Biochemistry, bDepartment of Molecular, Cellular, and Developmental Biology, and cCooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, CO 80309 Edited by Paul G. Falkowski, Rutgers, The State University of New Jersey, New Brunswick, NJ, and approved June 14, 2013 (received for review March 14, 2013) Pyruvate is an important “hub” metabolite that is a precursor for concentrations of many components (4). Fig. 1 shows an example in amino acids, sugars, cofactors, and lipids in extant metabolic net- which the availability of catalysts for different steps in a network works. Pyruvate has been produced under simulated hydrother- results in significantly different network topologies and accumu- mal vent conditions from alkyl thiols and carbon monoxide in the lation of different products. Network topology also depends on the presence of transition metal sulfides at 250 °C [Cody GD et al. set of reagents available and the concentrations of those reagents. K (2000) Science 289(5483):1337–1340], so it is plausible that pyru- For example, the network depicted in Fig. 1 would form only and M H J M vate was formed in hydrothermal systems on the early earth. We if no were available, and would form only and if the concentration of H were very high (assuming equal rate constants report here that pyruvate reacts readily in the presence of transi- D tion metal sulfide minerals under simulated hydrothermal vent for the partitioning of between the two possible pathways).
    [Show full text]
  • Introduction to Ionic Mechanisms Part I: Fundamentals of Bronsted-Lowry Acid-Base Chemistry
    INTRODUCTION TO IONIC MECHANISMS PART I: FUNDAMENTALS OF BRONSTED-LOWRY ACID-BASE CHEMISTRY HYDROGEN ATOMS AND PROTONS IN ORGANIC MOLECULES - A hydrogen atom that has lost its only electron is sometimes referred to as a proton. That is because once the electron is lost, all that remains is the nucleus, which in the case of hydrogen consists of only one proton. The large majority of organic reactions, or transformations, involve breaking old bonds and forming new ones. If a covalent bond is broken heterolytically, the products are ions. In the following example, the bond between carbon and oxygen in the t-butyl alcohol molecule breaks to yield a carbocation and hydroxide ion. H3C CH3 H3C OH H3C + OH CH3 H3C A tertiary Hydroxide carbocation ion The full-headed curved arrow is being used to indicate the movement of an electron pair. In this case, the two electrons that make up the carbon-oxygen bond move towards the oxygen. The bond breaks, leaving the carbon with a positive charge, and the oxygen with a negative charge. In the absence of other factors, it is the difference in electronegativity between the two atoms that drives the direction of electron movement. When pushing arrows, remember that electrons move towards electronegative atoms, or towards areas of electron deficiency (positive, or partial positive charges). The electron pair moves towards the oxygen because it is the more electronegative of the two atoms. If we examine the outcome of heterolytic bond cleavage between oxygen and hydrogen, we see that, once again, oxygen takes the two electrons because it is the more electronegative atom.
    [Show full text]
  • Pentachloride Hazard Summary Identification
    Common Name: PHOSPHORUS PENTACHLORIDE CAS Number: 10026-13-8 RTK Substance number: 1525 DOT Number: UN 1806 Date: August 1999 ----------------------------------------------------------------------- ----------------------------------------------------------------------- HAZARD SUMMARY * Phosphorus Pentachloride can affect you when breathed * Exposure to hazardous substances should be routinely in. evaluated. This may include collecting personal and area * Phosphorus Pentachloride is a CORROSIVE air samples. You can obtain copies of sampling results CHEMICAL and contact can severely irritate and burn the from your employer. You have a legal right to this skin and eyes with possible eye damage. information under OSHA 1910.1020. * Breathing Phosphorus Pentachloride can irritate the nose * If you think you are experiencing any work-related health and throat. problems, see a doctor trained to recognize occupational * Breathing Phosphorus Pentachloride can irritate the diseases. Take this Fact Sheet with you. lungs causing coughing and/or shortness of breath. Higher exposures can cause a build-up of fluid in the lungs WORKPLACE EXPOSURE LIMITS (pulmonary edema), a medical emergency, with severe OSHA: The legal airborne permissible exposure limit shortness of breath. (PEL) is 1 mg/m3 averaged over an 8-hour * Exposure to Phosphorus Pentachloride can cause workshift. headache, dizziness, weakness, nausea and vomiting. * Phosphorus Pentachloride may damage the liver and NIOSH: The recommended airborne exposure limit is kidneys. 1 mg/m3 averaged over a 10-hour workshift. * Phosphorus Pentachloride is a REACTIVE CHEMICAL and an EXPLOSION HAZARD. ACGIH: The recommended airborne exposure limit is 0.85 mg/m3 averaged over an 8-hour workshift. IDENTIFICATION Phosphorus Pentachloride is a white to pale yellow, WAYS OF REDUCING EXPOSURE crystalline solid with a pungent odor.
    [Show full text]
  • Infrared Spectroscopy of Protonated Acetic Acid
    Probing Elusive Cations: Infrared Spectroscopy of Protonated Acetic Acid Julia A. Davies,a) Nicholas A. Besley,b) Shengfu Yanga) and Andrew M. Ellisa),* a) Department of Chemistry, University of Leicester, University Road, Leicester, LE1 7RH, UK b) School of Chemistry, University of Nottingham, University Park, Nottingham, NG7 2RD, UK *Corresponding author: Email: [email protected] Manuscript submitted to The Journal of Physical Chemistry Letters 1 Abstract Protonated carboxylic acids, (RCOOH)H+, are the initial intermediates in acid-catalyzed (Fischer) esterification reactions. However the identity of the isomeric form is under debate. Surprisingly, no optical spectra have been reported for any isomer of the protonated carboxylic acid monomer, despite it being a fundamental organic cation. Here, we address these issues by using a new approach to prepare cold He-tagged cations of protonated acetic acid (AA), which entails electron ionization of helium nanodroplets containing metastable dimers of AA. The protonated species is subsequently probed using infrared photodissociation spectroscopy and, following a comparison with calculations, we identify the two isomers whose roles are debated in Fischer esterification. These are the carbonyl-protonated E,Z isomer and the metastable hydroxyl-protonated isomer. Our technique provides a novel approach that can be applied to other elusive ionic species. TOC Graphic 2 The mechanism of the acid-catalyzed (Fischer) esterification of carboxylic acids was first explored in detail in the 1930s.1,2 This early mechanistic work suggested that initial protonation occurs at the hydroxyl oxygen atom. In the case of an acetic acid monomer (AA), this leads to formation of the structure labelled as prot-OH in Figure 1.
    [Show full text]
  • Protonation Patterns in Reduced and Oxidized Forms of Electron Transfer Proteins
    Protonation patterns in reduced and oxidized forms of electron transfer proteins Dissertation For the award of the degree “doctor rerum naturalium” Division of Mathematics and Natural Sciences of the Georg-August-Universit¨at G¨ottingen submitted by Plamen Dobrev from Harmanli G¨ottingen 2012 Prof. Dr. Helmut Grubm¨uller (Reviewer) Department of Theoretical and Computational Biophysics, Max Planck In- stitute for Biophysical Chemistry G¨ottingen Prof. Dr. Marcus M¨uller (Reviewer) Institute for Theoretical Physics, Georg August University G¨ottingen Prof. Dr. Claudia Steinem Institute for Organic and Biomolecular Chemistry, Georg August University G¨ottingen Date of the oral examination: 08.05.2012 1 It is declared that the presented thesis has been written independently and with no other sources and aids than quoted. G¨ottingen, 10.04.2012 Plamen Dobrev 2 Contents 1 Introduction 6 2 Theory and Methods 13 2.1 Moleculardynamics........................ 13 2.2 pKa calculations of an acid in solution . 15 2.3 Free Energy calculation of deprotonation of an amino acid in MDsimulation .......................... 17 2.4 pKa calculation of ionizable groups in proteins using constant pHMD .............................. 19 2.5 Construction of the model compounds and the titratable amino acidsintheprotein ........................ 23 2.5.1 Residues with Carboxyl titratable group . 24 2.5.2 Histidine . 26 2.5.3 Tyrosine.......................... 27 2.5.4 Modelcompounds.. .. 27 2.6 Keeping the simulation box neutral upon protonation or de- protonation ............................ 29 2.6.1 Thechangeoftheionicstrength. 29 2.6.2 Restraing the coupled water molecules and the entropy change due tothe restraining potential . 30 3 2.6.3 Distance between the titrating site and the coupled watermolecule .....................
    [Show full text]
  • George A. Olah 151
    MY SEARCH FOR CARBOCATIONS AND THEIR ROLE IN CHEMISTRY Nobel Lecture, December 8, 1994 by G EORGE A. O L A H Loker Hydrocarbon Research Institute and Department of Chemistry, University of Southern California, Los Angeles, CA 90089-1661, USA “Every generation of scientific men (i.e. scientists) starts where the previous generation left off; and the most advanced discov- eries of one age constitute elementary axioms of the next. - - - Aldous Huxley INTRODUCTION Hydrocarbons are compounds of the elements carbon and hydrogen. They make up natural gas and oil and thus are essential for our modern life. Burning of hydrocarbons is used to generate energy in our power plants and heat our homes. Derived gasoline and diesel oil propel our cars, trucks, air- planes. Hydrocarbons are also the feed-stock for practically every man-made material from plastics to pharmaceuticals. What nature is giving us needs, however, to be processed and modified. We will eventually also need to make hydrocarbons ourselves, as our natural resources are depleted. Many of the used processes are acid catalyzed involving chemical reactions proceeding through positive ion intermediates. Consequently, the knowledge of these intermediates and their chemistry is of substantial significance both as fun- damental, as well as practical science. Carbocations are the positive ions of carbon compounds. It was in 1901 that Norris la and Kehrman lb independently discovered that colorless triphe- nylmethyl alcohol gave deep yellow solutions in concentrated sulfuric acid. Triphenylmethyl chloride similarly formed orange complexes with alumi- num and tin chlorides. von Baeyer (Nobel Prize, 1905) should be credited for having recognized in 1902 the salt like character of the compounds for- med (equation 1).
    [Show full text]