DOCSLIB.ORG

Functional Group-Selective Ion-Molecule Reactions of Ethylene Glycol and Its Monomethyl and Dimethyl Ethers

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Functional Group-Selective Ion-Molecule Reactions of Ethylene Glycol and Its Monomethyl and Dimethyl Ethers Functional Group-Selective Ion-Molecule Reactions of Ethylene Glycol and Its Monomethyl and Dimethyl Ethers Erika S. Eichmann and Jennifer S. Brodbelt Department of Chemistry and Biochemistry, University of Texas, Austin, Texas, USA The selective methylation and methylene substitution reactions of dimethyl ether ions with ethylene glycol, ethylene glycol monomethyl ether, and ethylene glycol dimethyl ether were investigated in a quadrupole ion trap mass spectrometer. Whereas the reactions of ethylene glycol and ethrlene glycol monomethyl ether with the methoxymethylene cation 45+ gave only [M + 13] product ions, the reaction of ethylene glycol dimethyl ether with the same reagent ion yielded exclusively [M + 15]+ ions. The relative rates of formation of these products and those from competing reactions were examined and rationalized on the basis of structural and electronic considerations, The heats of formation for various relevant species were estimated by computational methods and showed that the reactions leading to the [M + 13]+ ions were more energetically favorable than those leading to the [M + 15]+ products for cases in which both reactions are possible. Finally, the collision-induced dissociation behavior of the [M + H]+, [M + 13]+, and [M + 15]+ ions indicated that the [M + H]+ and [M + 15]+ ions dissociated by analogous pathways and were thus struc­ turally similar, whereas the [M + 13]+ ions possessed distinctly different structural charac­ teristics. (J Am Soc Mass Spectrom 1993,4,97-105) he importance of functional group interactions bilities, associative properties, and the favorabilities of and substituent effects in determining the out­ competitive dissociative channels of various types of Tcomes of reactions both in solution [1-4] and in ions with a variety of functional groups [1-14,16,17]. the gas phase has long been recognized [5-8]. For An understanding of such functional group interac­ example, the interactions between various functional tions is important not only from a physical organic groups in diol [9], diacid [10], diester [11], and other perspective in predicting reaction outcomes and mech­ simple systems [12~14] have been shown to have im­ anisms but also from a biological standpoint, For ex­ portant consequences on the physical properties and ample, hydroxyl groups and ether linkages are among reactive and dissociative patterns of these ions. In the most ubiquitous functional groups [181, and virtu­ some cases, remote group participation can promote ally all possible combinations, relative positions, and reactive channels inaccessible to related molecules orientations of these functionalities can be found in lacking the interaction [15]. The converse is also true: sugars, steroids, antibiotics, and other biologically rele­ The presence of an additional functional group can vant molecules. prevent certain reactions, either through steric or elec­ Mass spectrometric methods have been increasingly tronic interactions or by promotion of competition be­ applied to the characterization of such types of tween reactions that would otherwise be expected to biomolecules; however, the structural elucidation of predominate. these complex molecules remains deficient. The devel­ The type and extent of interaction and consequent opment of activation techniques, such as collision­ enhancement or inhibition of the reactions naturally induced dissociation [19] and surface-induced dissoci­ depends on the nature, position, and orientation of all ation [20], for promoting fragmentations of functional groups involved. The large body of previ­ biomolecules in characteristic patterns has assisted in ous work in this area has helped to establish generally solving this problem. The design of selective accepted correlations of functional group interactions ion-molecule reactions also holds promise for reveal­ with gas-phase basicities and proton affinities, ion sta- ing structurally diagnostic information. Chemical ion­ ization [21, 22] reactions with novel reagent gases have been shown to offer great potential, and tremendous interest has therefore been stimulated in the characteri­ Address reprint requests to jennifer s. Brodbelt, Department of Chemistry and Biochemistry, University of Texas, Austin, IX 7B712. zation of new site-selective reagents [23]. © 1993 American Society for Mass Spectrometry Received June 29,1992 1044-0305/93/$6.00 Revised September 25, 1992 Accepted September 26, 1992 98 EICHMANN AND BRODBELT J Am Soc Mass Spectrom 1993,4,97-105 We are particularly concerned with the develop­ Results and Discussion ment of site-specific reactions for characterization of antibiotics, and a firm understanding of the fundamen­ Comparison of Reactions tal reactions between the common substituents is Two reactive ions are typically formed on ionization of therefore a necessity. We have undertaken this study DME-the methoxymethylene cation (1) and the proto­ of simple disubstituted ethanes to illustrate that the nated DME (2). Previous studies in our group [24, 31] reactive and dissociative properties of structurally and have shown that on reaction with the ions of mr z 45 electronically similar ions can be dramatically differ­ and 47 from DME, substrates typically yield one or ent. To correlate and contrast the reactivities of more of several product ions, depending on the nature, methoxyl and hydroxyl groups, we have compared the position, and orientation of their functional groups: ion-molecule reactions of dimethyl ether ions with [M + 1]+, [M + 13]+, [M + 15]+, [M + 45]+, and [M ethylene glycol and its mono- and diethers and exam­ + 47]+. Although the [M + 45]4 and [M + 47]+ ined the formation mechanisms for each product adduct ions, or collision complexes, are not always observed. In addition, we have made a qualitative observable in the ion trap, previous work has demon­ comparison of the formation rates and relative favora­ strated that the [M + 1]+, [M + 13]+, and [M + 15]+ bilities of formation for the observed products and ions all originate directly from these ions [12, 31]. investigated the thermodynamic properties that pre­ sumably govern the reactions observed. The two reactions of interest in this study are meth­ ylene substitution and methyl cation attachment. The former has been recently described for other small organic systems [9, 12, 24]. The methyl cation attach­ ment process has also lately been of interest in studies concerning sites of electrophilic additions [25-27]. 1 2 Experimental The [M + 1]+ ions arise predominantly from simple A Finnigan ion trap mass spectrometer (Finnigan-MAT, proton transfer from the protonated DME molecule San Jose, CA) [28, 29] was used for all experiments. (m/z 47) to the substrate. These products presumably The samples (Aldrich Chemical Co., Milwaukee, WI) arise through initial formation of a proton-bound colli­ were introduced through a heated leak valve system, sion complex at [M + 47]+, which fragments to give and typical pressures used were 1.3 X 10-4 Pa. the protonated analyte (Scheme Ia), In most of the Dimethyl ether (DME) (MG Industries, Valley Forge, systems studied to date in our laboratory, including PA) reagent gas pressure was generally 1.2 X 10-3 Pa, the three systems under study here, the proton affini­ and helium buffer gas was admitted at approximately ties of the substrates have exceeded that of the neutral 0.13 Pa. The ions produced by electron ionization of DME. Therefore, dissociation of the loosely bound [M DME were stored and reacted with the neutral sample + 47)+ collision complex generally gives preferentially vapor. The ion-molecule reaction times were varied the [M + 1]+ product ion. between 0 and SOD ms. Alternately, individual reagent Likewise, the [M + 13)+ and [M + 15]+ ions have gas ions were trapped and isolated by application of been shown to result from fragmentation of an [M + appropriate radiofrequency and de voltages [30] and 45]+ adduct that arises from the collision complex allowed to react with the neutral analyte molecules for formed between the neutral analyte and the DME varying periods of time (0-500 ms), In either case, the reagent ion at mjz 45 [12]. The complex either rear­ ions formed were selectively isolated, and activated to ranges to allow transfer of a methyl group to the produce collision-induced dissociation (ClD) spectra. substrate (Scheme Ib, upper path) and simultaneous All thermochemical values not available in the liter­ loss of formaldehyde or undergoes a different rear­ ature were estimated by computer calculations. The rangement followed by loss of methanol (Scheme Ib, computational programs PCMODEL and MOPAC were lower path), resulting in a net substitution of a methy­ obtained from Serena Software (Bloomington, IN) and lene group onto the substrate. were run on a Macintosh Ilsi personal computer. The For ethylene glycol, ethylene glycol monomethyl molecular modeling program PCMODEL was first used ether, and ethylene glycol DME, the [M + 45]+ and to approximate the minimum-energy structure, and [M + 47]+ ions are not directly observable, presum­ the resulting coordinates were entered into the ably because they are formed with excessive internal serniempirical program MOPAC. The AMI Hamilton­ energy and are not sufficiently deactivated by colli­ ian operator and default parameters were used in all sions with the helium buffer gas. Rather, they dissoci­ cases. Calculations were performed at least three times, ate spontaneously on formation, giving [M + 1]+, [M and consistent values were obtained. + 13)+, and [M + 15]+ product ions. J Am Soc Mass Spectrom 1993, 4, 97-105 ION-MOLECULE REACTIONS OF ETHYLENE GLYCOL 99 (M+H)' H M 6+ />. ... H ....... 'CH 3C 3 HO:). 1Ic:J n [)J H~C/O""""CH3 H-O+ 0 H2C <:> (1.4+47)' 47' Collision Complex 101 kcal/mol 99 kcal/rnol a a (M+ 1:3)+ + CH30H 0+ /" M "'0+ r>: H2C~ ......CH3 ~ H2C~ <,CH~J CH30;). l 1Ic:J CH3-O,,-/On IM+ 15]" + CH,O "" H2C (M + 45)' 45' Collision Complex: 99 kcallmol 94 kcal/mol b b Scheme L Formation reactions for (a) [M + 1]+ and (b) [M + 131+ and [M + 15]+ product ions. Figure 1. Estimated heats of formation for the cyclized and uncyclized [M + 13]+ ions of (a) ethylene glycol and (b) ethylene glycol monomethyl ether.
Load more

Recommended publications
  • Chapter 21 the Chemistry of Carboxylic Acid Derivatives
    Instructor Supplemental Solutions to Problems © 2010 Roberts and Company Publishers Chapter 21 The Chemistry of Carboxylic Acid Derivatives Solutions to In-Text Problems 21.1 (b) (d) (e) (h) 21.2 (a) butanenitrile (common: butyronitrile) (c) isopentyl 3-methylbutanoate (common: isoamyl isovalerate) The isoamyl group is the same as an isopentyl or 3-methylbutyl group: (d) N,N-dimethylbenzamide 21.3 The E and Z conformations of N-acetylproline: 21.5 As shown by the data above the problem, a carboxylic acid has a higher boiling point than an ester because it can both donate and accept hydrogen bonds within its liquid state; hydrogen bonding does not occur in the ester. Consequently, pentanoic acid (valeric acid) has a higher boiling point than methyl butanoate. Here are the actual data: INSTRUCTOR SUPPLEMENTAL SOLUTIONS TO PROBLEMS • CHAPTER 21 2 21.7 (a) The carbonyl absorption of the ester occurs at higher frequency, and only the carboxylic acid has the characteristic strong, broad O—H stretching absorption in 2400–3600 cm–1 region. (d) In N-methylpropanamide, the N-methyl group is a doublet at about d 3. N-Ethylacetamide has no doublet resonances. In N-methylpropanamide, the a-protons are a quartet near d 2.5. In N-ethylacetamide, the a- protons are a singlet at d 2. The NMR spectrum of N-methylpropanamide has no singlets. 21.9 (a) The first ester is more basic because its conjugate acid is stabilized not only by resonance interaction with the ester oxygen, but also by resonance interaction with the double bond; that is, the conjugate acid of the first ester has one more important resonance structure than the conjugate acid of the second.
    [Show full text]
  • The Progression of Chiral Anions from Concepts to Applications in Asymmetric Catalysis Robert J
    REVIEW ARTICLE PUBLISHED ONLINE: 24 JULY 2012 | DOI: 10.1038/NCHEM.1405 The progression of chiral anions from concepts to applications in asymmetric catalysis Robert J. Phipps, Gregory L. Hamilton and F. Dean Toste* Despite the tremendous advances of the past four decades, chemists are far from being able to use chiral catalysts to con- trol the stereoselectivity of any desired reaction. New concepts for the construction and mode of operation of chiral catalysts have the potential to open up previously inaccessible reaction space. The recognition and categorization of distinct approaches seems to play a role in triggering rapid exploration of new territory. This Review both reflects on the origins as well as details a selection of the latest examples of an area that has advanced considerably within the past five years or so: the use of chiral anions in asymmetric catalysis. Defining reactions as involving chiral anions is a difficult task owing to uncertainties over the exact catalytic mechanisms. Nevertheless, we attempt to provide an overview of the breadth of reactions that could reasonably fall under this umbrella. 9 ithin the broader field of science, organic chemistry is Of significantly greater acidity (pKa around 2–4) are chiral phos- often referred to as a mature field of study. In spite of this, phoric acids, commonly derived from BINOL (1,1′-bi-2-naphthol). Wnew avenues of inquiry seem to arise with relative fre- These catalysts have risen to prominence over the past decade quency. Perhaps we take it for granted that expansions of the field because their high acidity permits activation of a broad range of are sparked when one or two chemical laboratories uncover a new substrates3,10.
    [Show full text]
  • Metabolic-Hydroxy and Carboxy Functionalization of Alkyl Moieties in Drug Molecules: Prediction of Structure Influence and Pharmacologic Activity
    molecules Review Metabolic-Hydroxy and Carboxy Functionalization of Alkyl Moieties in Drug Molecules: Prediction of Structure Influence and Pharmacologic Activity Babiker M. El-Haj 1,* and Samrein B.M. Ahmed 2 1 Department of Pharmaceutical Sciences, College of Pharmacy and Health Sciences, University of Science and Technology of Fujairah, Fufairah 00971, UAE 2 College of Medicine, Sharjah Institute for Medical Research, University of Sharjah, Sharjah 00971, UAE; [email protected] * Correspondence: [email protected] Received: 6 February 2020; Accepted: 7 April 2020; Published: 22 April 2020 Abstract: Alkyl moieties—open chain or cyclic, linear, or branched—are common in drug molecules. The hydrophobicity of alkyl moieties in drug molecules is modified by metabolic hydroxy functionalization via free-radical intermediates to give primary, secondary, or tertiary alcohols depending on the class of the substrate carbon. The hydroxymethyl groups resulting from the functionalization of methyl groups are mostly oxidized further to carboxyl groups to give carboxy metabolites. As observed from the surveyed cases in this review, hydroxy functionalization leads to loss, attenuation, or retention of pharmacologic activity with respect to the parent drug. On the other hand, carboxy functionalization leads to a loss of activity with the exception of only a few cases in which activity is retained. The exceptions are those groups in which the carboxy functionalization occurs at a position distant from a well-defined primary pharmacophore. Some hydroxy metabolites, which are equiactive with their parent drugs, have been developed into ester prodrugs while carboxy metabolites, which are equiactive to their parent drugs, have been developed into drugs as per se.
    [Show full text]
  • Methyl Substitution Effects on the Proton Chemical Shifts in Benzene *
    Methyl Substitution Effects on the Proton Chemical Shifts in Benzene * G. S. REDDY E. I. du Pont de Nemours & Company, Inc. Explosives Department, Eastern Laboratory, Gibbstown, New Jersey, U.S.A. (Z. Naturforschg. 21 a, 609—615 [1966] ; received 16 December 1965) Methyl substitution effects on aromatic and methyl proton chemical shifts in several mono-, di-, and trimethyl benzenes are studied. A new method for obtaining the changes in the ring proton chemical shifts from those of methyl proton shifts at the corresponding positions is used. The extra jr-electron densities in toluene are calculated using the already known relation between the jr-elec- tron densities and the proton shifts in aromatic systems. An inverse relationship is obtained between the ionization potentials and the total methyl effects on the chemical shifts in this series of com- pounds as one would expect. Dipole moment of toluene is calculated, and a reasonably good agree- ment is found between the experimentally observed and the calculated dipole moment. Several efforts have been made from time to Considerable work has also been done in estimat- time to study the substitution effects on chemical ing ir-electron densities from chemical shift meas- shifts and coupling constants. One of the earliest urements in unsaturated systems. This study in- attempts in this line are those of CAVANAUGH and volves extension of the substitution effects and also DAILEY 1 who tried to study the effect of multiple estimating jr-electron densities in methyl benzenes. methyl substitution in methane. They encountered Eight mono-, di-, and trimethyl substituted benzenes negative shifts contrary to expectations based on have been studied, and a new technique has been inductive and hyperconjugative effects of the methyl deployed to obtain the methyl substitution effects group which eventually was attributed to the an- on the chemical shifts of ring protons from proton isotropy effect of the added C — C bonds 2-7.
    [Show full text]
  • Organic Chemistry
    Wisebridge Learning Systems Organic Chemistry Reaction Mechanisms Pocket-Book WLS www.wisebridgelearning.com © 2006 J S Wetzel LEARNING STRATEGIES CONTENTS ● The key to building intuition is to develop the habit ALKANES of asking how each particular mechanism reflects Thermal Cracking - Pyrolysis . 1 general principles. Look for the concepts behind Combustion . 1 the chemistry to make organic chemistry more co- Free Radical Halogenation. 2 herent and rewarding. ALKENES Electrophilic Addition of HX to Alkenes . 3 ● Acid Catalyzed Hydration of Alkenes . 4 Exothermic reactions tend to follow pathways Electrophilic Addition of Halogens to Alkenes . 5 where like charges can separate or where un- Halohydrin Formation . 6 like charges can come together. When reading Free Radical Addition of HX to Alkenes . 7 organic chemistry mechanisms, keep the elec- Catalytic Hydrogenation of Alkenes. 8 tronegativities of the elements and their valence Oxidation of Alkenes to Vicinal Diols. 9 electron configurations always in your mind. Try Oxidative Cleavage of Alkenes . 10 to nterpret electron movement in terms of energy Ozonolysis of Alkenes . 10 Allylic Halogenation . 11 to make the reactions easier to understand and Oxymercuration-Demercuration . 13 remember. Hydroboration of Alkenes . 14 ALKYNES ● For MCAT preparation, pay special attention to Electrophilic Addition of HX to Alkynes . 15 Hydration of Alkynes. 15 reactions where the product hinges on regio- Free Radical Addition of HX to Alkynes . 16 and stereo-selectivity and reactions involving Electrophilic Halogenation of Alkynes. 16 resonant intermediates, which are special favor- Hydroboration of Alkynes . 17 ites of the test-writers. Catalytic Hydrogenation of Alkynes. 17 Reduction of Alkynes with Alkali Metal/Ammonia . 18 Formation and Use of Acetylide Anion Nucleophiles .
    [Show full text]
  • Aldehydes and Ketones
    12 Aldehydes and Ketones Ethanol from alcoholic beverages is first metabolized to acetaldehyde before being broken down further in the body. The reactivity of the carbonyl group of acetaldehyde allows it to bind to proteins in the body, the products of which lead to tissue damage and organ disease. Inset: A model of acetaldehyde. (Novastock/ Stock Connection/Glow Images) KEY QUESTIONS 12.1 What Are Aldehydes and Ketones? 12.8 What Is Keto–Enol Tautomerism? 12.2 How Are Aldehydes and Ketones Named? 12.9 How Are Aldehydes and Ketones Oxidized? 12.3 What Are the Physical Properties of Aldehydes 12.10 How Are Aldehydes and Ketones Reduced? and Ketones? 12.4 What Is the Most Common Reaction Theme of HOW TO Aldehydes and Ketones? 12.1 How to Predict the Product of a Grignard Reaction 12.5 What Are Grignard Reagents, and How Do They 12.2 How to Determine the Reactants Used to React with Aldehydes and Ketones? Synthesize a Hemiacetal or Acetal 12.6 What Are Hemiacetals and Acetals? 12.7 How Do Aldehydes and Ketones React with CHEMICAL CONNECTIONS Ammonia and Amines? 12A A Green Synthesis of Adipic Acid IN THIS AND several of the following chapters, we study the physical and chemical properties of compounds containing the carbonyl group, C O. Because this group is the functional group of aldehydes, ketones, and carboxylic acids and their derivatives, it is one of the most important functional groups in organic chemistry and in the chemistry of biological systems. The chemical properties of the carbonyl group are straightforward, and an understanding of its characteristic reaction themes leads very quickly to an understanding of a wide variety of organic reactions.
    [Show full text]
  • Ethylene Dichloride (Edc) Handbook
    ETHYLENE DICHLORIDE (EDC) HANDBOOK OXYCHEM TECHNICAL INFORMATION 11/2014 Dallas-based Occidental Chemical Corporation is a leading North American manufacturer of basic chemicals, vinyls and performance chemicals directly and through various affiliates (collectively, OxyChem). OxyChem is also North America's largest producer of sodium chlorite. As a Responsible Care® company, OxyChem's global commitment to safety and the environment goes well beyond compliance. OxyChem's Health, Environment and Safety philosophy is a positive motivational force for our employees, and helps create a strong culture for protecting human health and the environment. Our risk management programs and methods have been, and continue to be, recognized as some of the industry's best. OxyChem offers an effective combination of industry expertise, experience, on line business tools, quality products and exceptional customer service. As a member of the Occidental Petroleum Corporation family, OxyChem represents a rich history of experience, top-notch business acumen, and sound, ethical business practices. 1 Table of Contents Page Introduction to Ethylene Dichloride ............................................................................................................ 3 Manufacturing .................................................................................................................................................. 3 Ethylene Dichloride (EDC) — Uses ................................................................................................................
    [Show full text]
  • ETHYLENE GLYCOL: Environmental Aspects
    This report contains the collective views of an international group of experts and does not necessarily represent the decisions or the stated policy of the United Nations Environment Programme, the International Labour Organisation, or the World Health Organization. Concise International Chemical Assessment Document 22 ETHYLENE GLYCOL: Environmental aspects First draft prepared by Dr S. Dobson, Institute of Terrestrial Ecology, Natural Environment Research Council, Huntingdon, United Kingdom Please note that the layout and pagination of this pdf file are not identical to those of the printed CICAD Published under the joint sponsorship of the United Nations Environment Programme, the International Labour Organisation, and the World Health Organization, and produced within the framework of the Inter-Organization Programme for the Sound Management of Chemicals. World Health Organization Geneva, 2000 The International Programme on Chemical Safety (IPCS), established in 1980, is a joint venture of the United Nations Environment Programme (UNEP), the International Labour Organisation (ILO), and the World Health Organization (WHO). The overall objectives of the IPCS are to establish the scientific basis for assessment of the risk to human health and the environment from exposure to chemicals, through international peer review processes, as a prerequisite for the promotion of chemical safety, and to provide technical assistance in strengthening national capacities for the sound management of chemicals. The Inter-Organization Programme for the Sound Management of Chemicals (IOMC) was established in 1995 by UNEP, ILO, the Food and Agriculture Organization of the United Nations, WHO, the United Nations Industrial Development Organization, the United Nations Institute for Training and Research, and the Organisation for Economic Co-operation and Development (Participating Organizations), following recommendations made by the 1992 UN Conference on Environment and Development to strengthen cooperation and increase coordination in the field of chemical safety.
    [Show full text]
  • Toxicological Profile for Ethylbenzene
    ETHYLBENZENE 151 5. PRODUCTION, IMPORT/EXPORT, USE, AND DISPOSAL 5.1 PRODUCTION Ethylbenzene is primarily produced by the alkylation of benzene with ethylene in liquid-phase slurry reactors promoted with aluminum chloride catalysts or by vapor-phase reaction of benzene with dilute ethylene-containing feedstock with a boron trifluoride catalyst supported on alumina (Cannella 2007; Clayton and Clayton 1981; HSDB 2009; Welch et al. 2005; Ransley 1984). Newer versions of the method employ synthetic zeolites in fixed-bed reactors as catalysts for alkylation in the liquid phase or narrow pore synthetic zeolites in fixed-bed reactors in the vapor phase (Welch et al. 2005). Other methods of manufacturing ethylbenzene include preparation from acetophenone, dehydrogenation of naphthenes, catalytic cyclization and aromatization, separation from mixed xylenes via fractionation, reaction of ethylmagnesium bromide and chlorobenzene, extraction from coal oil, and recovery from benzene-toluene-xylene (BTX) processing(Clayton and Clayton 1981; HSDB 2009; Ransley 1984; Welch et al. 2005). Commercial grades of ethylbenzene may contain small amounts of m-xylene, p-xylene, cumene, and toluene (HSDB 2009). Ethylbenzene is traditionally ranked as one of the top 50 chemicals produced in the United States. Table 5-1 shows the historical production volumes of ethylbenzene from 1983 to 2005 (C&EN 1994a, 1994b, 1995, 2006; Kirschner 1995). Table 5-2 lists the facilities in each state that manufacture or process ethylbenzene, the intended use, and the range of maximum amounts of ethylbenzene that are stored on site. There are currently 3,755 facilities that produce, process, or use ethylbenzene in the United States. The data listed in Table 5-2 are derived from the Toxics Release Inventory (TRI06 2008).
    [Show full text]
  • Functional Groups Kimberly Hatch Harrison
    Functional Groups Kimberly Hatch Harrison Functional groups are those small chemical species you see hanging off the outside of a molecule. Just a handful of these functional groups de- termine most of the chemical reactions that happen between biological molecules. If you memorize the chemical behavior of these functional groups, you’ll be able to predict what kinds of reactions biological molecules can do. You can’t open a lock with a screwdriver–the shape of a screwdriver is quite different from a key, which means it has a dif- ferent function. "Form determines function" is something you’ll hear over and over in biochemistry, and that’s because it’s true. The over- all 3-dimensional shape of a molecule allows it to fit into another molecule, like how a key fits into a lock. But not all keys are the same. You have to look closely at the teeth of a key to see which lock it can open. Similarly, you need to look at the details of the outside of a molecule to understand what kinds of chemical interactions it can do with other molecules. How the carbon skeleton of a biological molecule is folded up de- termines its general 3D shape. So that’s one level of understanding– this molecule looks like a key, this one looks like a lock, etc. But then you must look closer, at the surface details, to understand exactly which key, exactly what kind of lock. When you examine the outside of a biological molecule, you can identify which functional groups are standing out on its surface, like little flags.
    [Show full text]
  • Ethylene Glycol Ingestion Reviewer: Adam Pomerlau, MD Authors: Jeff Holmes, MD / Tammi Schaeffer, DO
    Pediatric Ethylene Glycol Ingestion Reviewer: Adam Pomerlau, MD Authors: Jeff Holmes, MD / Tammi Schaeffer, DO Target Audience: Emergency Medicine Residents, Medical Students Primary Learning Objectives: 1. Recognize signs and symptoms of ethylene glycol toxicity 2. Order appropriate laboratory and radiology studies in ethylene glycol toxicity 3. Recognize and interpret blood gas, anion gap, and osmolal gap in setting of TA ingestion 4. Differentiate the symptoms and signs of ethylene glycol toxicity from those associated with other toxic alcohols e.g. ethanol, methanol, and isopropyl alcohol Secondary Learning Objectives: detailed technical/behavioral goals, didactic points 1. Perform a mental status evaluation of the altered patient 2. Formulate independent differential diagnosis in setting of leading information from RN 3. Describe the role of bicarbonate for severe acidosis Critical actions checklist: 1. Obtain appropriate diagnostics 2. Protect the patient’s airway 3. Start intravenous fluid resuscitation 4. Initiate serum alkalinization 5. Initiate alcohol dehydrogenase blockade 6. Consult Poison Center/Toxicology 7. Get Nephrology Consultation for hemodialysis Environment: 1. Room Set Up – ED acute care area a. Manikin Set Up – Mid or high fidelity simulator, simulated sweat if available b. Airway equipment, Sodium Bicarbonate, Nasogastric tube, Activated charcoal, IV fluid, norepinephrine, Simulated naloxone, Simulate RSI medications (etomidate, succinylcholine) 2. Distractors – ED noise For Examiner Only CASE SUMMARY SYNOPSIS OF HISTORY/ Scenario Background The setting is an urban emergency department. This is the case of a 2.5-year-old male toddler who presents to the ED with an accidental ingestion of ethylene glycol. The child was home as the father was watching him. The father was changing the oil on his car.
    [Show full text]
  • ETHYLENE from METHANE (January 1994)
    Abstract Process Economics Program Report No. 208 ETHYLENE FROM METHANE (January 1994) This report evaluates two routes for the production of ethylene from methane: the direct synthesis based on the oxidative coupling of methane, and the less direct chemistry of converting methanol (which is derived from methane via synthesis gas) in the presence of an aluminophosphate molecular sieve catalyst. Our evaluations indicate that at the present state of development, the economics of both routes are unattractive when compared with the steam pyrolysis of hydrocarbons. We analyze the results of our evaluations to define the technical targets that must be attained for success. We also present a comprehensive technical review that examines not only the two routes evaluated, but also some of the more promising alternative approaches, such as synthesis gas conversion via a modified Fischer-Tropsch process, ethanol synthesis by the homologation of methanol, and ethylene production via methyl chloride. This report will be of interest to petrochemical companies that produce or consume ethylene and to energy-based companies (or equivalent government organizations in various countries) that have access to or control large resources of methane-rich natural gas. PEP’91 SCN CONTENTS 1 INTRODUCTION 1-1 2 SUMMARY 2-1 TECHNICAL REVIEW 2-1 Oxidative Coupling 2-1 Methanol Conversion to Ethylene 2-3 Modified Fischer-Tropsch (FT) Process 2-3 Methanol Homologation 2-3 Conversion via Methyl Chloride 2-4 SRI’S PROCESS CONCEPTS 2-4 Ethylene from Methane by Oxidative
    [Show full text]