DOCSLIB.ORG

Odor and Flavor Responses to Additives in Edible Oils 1

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Odor and Flavor Responses to Additives in Edible Oils 1 2988 Reprinted from the JOURNAL OF THE AMERICA.." OIL CHEMISTS' SOCIETY, Vol. 48, No.9, Pages: 495-498 (1971) "Purchased by U.S. Department of Agriculture for Official Use." Odor and Flavor Responses to Additives in Edible Oils 1 C.D. EVANS, HELEN A. MOSER and G.R. LIST, Northern Regional Research LaboratorY,2 Peoria, Illinois 61604 ABSTRACT pounds, including unsaturated esters, ketones, alcohols and The odor threshold was determined for a series of hydrocarbons, arose from hydroperoxide breakdown and unsaturated ketones, secondary alcohols, hydro­ could contribute to an autoxidized flavor. In the past carbons and substituted furans added to bland edible decade both vinyl amyl ketone and vinyl ethyl ketone oil. Odor thresholds were taken as the point where (9-11) and their alcohol counterparts (5,9,12) have been 50% of a 15- to 18-member taste panel could detect isolated from autoxidized fats and shown to contribute an odor difference from the control oil. These undesirable flavor components. additives are oxidative products of fats, but the Although various hydrocarbons have been isolated from concentrations investigated were far below any level autoxidized and irradiated fats, they reportedly have associated with an identifying odor or taste of the generally weak flavors. Forss (3) indicates contamination additive per se. Odor, rather than flavor, was selected with alcohols or mercaptans as the source of hydrocarbon as the starting basis because of greater acuity and ease flavor. Smouse et al. (13) demonstrated that I-decyne was a of handling a large number of samples with less taster major component in the volatile products of slightly fatigue. Oil samples containing additive concentra­ oxidized soybean oil. This alkyne, they stated, has a tions near the odor threshold levels were evaluated by threshold of 0.1 ppm. The presence of alkynes and flavor score and flavor descriptions. Taste panel unsaturated hydrocarbons in autoxidized and irradiated fats members were experienced oil tasters and were has been recorded by various investigators (14-18). allowed free choice in selecting terms to describe the The formation of alkadienes upon irradiation of beef flavor quality of the oil samples. The propyl and and pork fat has been reported by Champagne and Nawar butyl members of the homologous series of vinyl (14). They indicated that the l-alkenes were the most ketones had the lowest odor thresholds, whereas the highly odorous compounds of the series of alkane, alkene, difference in odor threshold was small between alkyne and diene hydrocarbons investigated. homologs in the unsaturated alcohols and in the 2 Chang and coworkers (19,20) isolated pentyl furan from substituted furans. Vinyl propyl ketone, vinyl propyl oxidized soybean oil. They believe that this substance carbinol (1-hexen-3-01) and 2-propyl furan had odor imparts the characteristic beany odor and flavor reminis­ thresholds of 0.005, 0.5 and 6 ppm, respectively. cent of "reverted" soybean oil at concentrations of I to 10 Odor thresholds of the unsaturated hydrocarbons are ppm. markedly lower than those of the saturated isologs. Since information on how nonaldehydic volatile com­ The odor of nonane can be detected at 650 ppm. ponents contribute to flavor is confusing and contradictory, However, at 1000 ppm it cannot be tasted and oils we undertook a study to evaluate carefully the odor containing it were scored equal to the control oil. threshold of numerous compounds, other than aldehydes, I-Nonene, l-nonyne and other tested C-9 unsaturated that are products of fat autoxidation. hydrocarbons, including a number of dienes, have odor thresholds of about 10 ppm. The hydrocarbons EXPERIMENTAL PROCEDURES l-hexyne, l-nonyne and l-decyne had odor thresh­ olds of 0.2,5 and 4 ppm, respectively. Chemicals of the highest purity available were obtained from several sources (Table 0. The purity was checked by gas chromatography and all materials proved to be 98% INTRODUCTION pure or better. A number of the diene samples were When it comes to taste and odor sensations, we are all purchased as special synthesis products. Some of the distinct individualists. Only through experience with food samples of vinyl and allyl ketones and their corresponding and our environment do we gain and acquire a knowledge alcohols were synthesized in our own laboratory by the of taste and smell. The classification of flavor is strictly a procedures of Brown and Garg (21) and of Crabalona (22). descriptive terminology based on an individual's perception The method of Amoore (23) and that of Patton and and memory. Most individuals have acute odor perception, Josephson (24) were investigated as a technique to deter­ as well as the ability to identify different aromas. Off­ mine the odor threshold of several compounds dissolved in flavors in bland foods, for example, are often described in freshly deodorized cottonseed salad oil. With a 20-member terms of distinctive odors rather than distinctive tastes. panel the time involved with Amoore's method was Descriptive terminology characterizing off-flavored fats as excessive although it will give a more reproducible and cardboardy, trainy, painty, skunky and rubbery illustrates accurate threshold because of its chance probability of 1 in the reliance on odor memory. Although odor perception 10. By modifying Patton and Josephson's method slightly has generally been regarded as being more sensitive than in the plotting of taster results, the greater accuracy of taste, we and others (1,2) found that when simple odorous Amoore's method was partially attained. Our modified compounds are added to fats, the taste threshold is equal to procedure consists of presenting each taster with five or greater than the individual's odor perception. samples, in random order, in which the minimum concen­ The contribution of saturated and unsaturated aldehydes tration difference between samples is twofold. The geo­ to off-flavor characteristics of fats has been well established metric scale of concentration (binary dilution) was carried by many investigators (3-6). Badings (7) in his review in out in all sets of dilutions. Samples (7.5 m!) of cottonseed 1960 states that ketones are unimportant in their contribu­ oil containing the appropriate concentrations of the odor­ tion to oxidation off-flavors. Later, Evans (8), discussing ant were presented to the taster in 150 ml beakers covered autoxidation of fats, indicated that many volatile com- with watch glasses. The samples were warmed and served at 55 C by placing the five beakers in an aluminum block 1Presented at the AOeS Meeting, New Orleans, April 1970. heated on a thermostatically controlled hot plate. Usually 2No. Market. Nutr. Res. Div., ARS, USDA. one sample served as a blank, but any number of blanks 495 496 JOURNAL OF THE AMERICAN OIL CHEMISTS' SOCIETY VOL. 48 may be used. In a preliminary run if the highest concentra­ ences. Threshold differences are more likely to result from tion was not detected by 80% of the panel, tests with higher taster variability and various methodologies than from concentrations were made. After the concentration range minor impurities in the standards. Guadagni et al. (25) was established, the tests were repeated to establish an report that sniffing a water solution of nonanal was a average threshold value, i.e., the point where 50% of the relatively insensitive method compared to their squirt bottle panel could detect the additive. In plotting the correct method with which they attained a threshold of 1 vs. 98 responses to 0 btain the average threshold value, only results ppb from sniffing. Since our odor studies were concerned were used of tasters who had correctly identified all the with edible oil evaluations, panel methodology was the higher concentration samples. Thus the results of a taster same in both odor and taste tests. who correctly identified the presence of the substance at Table I shows the odor detection threshold for a series concentrations of 16, 8 and 2 ppm but missed 4 and 0 of hydrocarbons, substituted furans, unsaturated ketones parts, would be used only in calculating the percentage and alcohols. Because thresholds of saturated aliphatic correct for 16 and 8 ppm. Odor thresholds are reported as hydrocarbons range about 1000 ppm, these hydrocarbons the average value of two to four complete panel evalua­ were not a part of our study. Unsaturation confers a high tions. odor potential to aliphatic hydrocarbons. Detection limits are lower by an order of two to three magnitudes from the RESULTS AND DISCUSSION saturated analogs. A triple bond lowers the threshold more The method used to determine the sensitivity threshold than a double bond and from limited data the difference may be important and could account for literature differ- can be as much as one order of magnitude. Sometimes, dienes have had significantly lower thresholds than mono­ TABLE I enes of the same carbon chain length. No consistent effect of conjugation, nonconjugation or terminal position of the Detection Odor Threshold of Additives to Cottonseed Oil double bonds could be observed with the limited number of samples investigated. In the series of 2,4-conjugated hexa­ Threshold,a Source of Compound ppm compoundb dienes, the cis,cis-geometrical isomer could be detected at 1/1 0 the concentration of either the cis,trans- or the Hydrocarbons trans, trans-isomer. .AJkanes Odor thresholds of less than 1 ppm are indicated for a 650 5 Nonane number of hydrocarbons, and apparently the six-carbon .AJkenes chain homolog has the lowest threshold in each series. I-Hexene 0.02 5 1-0ctene 2 5 Trace amounts of unsaturated hydrocarbons near these I-Nonene 9 5 threshold levels could modify the flavor response for any I-Decene 7 5 fat or fatty food where they may be present. Alkynes Odor thresholds of 2-substituted furans are, in general, I-Pentyne 0.7 4 comparable to the odor threshold levels of unsaturated I-Hexyne 0.2 4 hydrocarbons.
Load more

Recommended publications
  • 14.8 Organic Synthesis Using Alkynes
    14_BRCLoudon_pgs4-2.qxd 11/26/08 9:04 AM Page 666 666 CHAPTER 14 • THE CHEMISTRY OF ALKYNES The reaction of acetylenic anions with alkyl halides or sulfonates is important because it is another method of carbon–carbon bond formation. Let’s review the methods covered so far: 1. cyclopropane formation by the addition of carbenes to alkenes (Sec. 9.8) 2. reaction of Grignard reagents with ethylene oxide and lithium organocuprate reagents with epoxides (Sec. 11.4C) 3. reaction of acetylenic anions with alkyl halides or sulfonates (this section) PROBLEMS 14.18 Give the structures of the products in each of the following reactions. (a) ' _ CH3CC Na| CH3CH2 I 3 + L (b) ' _ butyl tosylate Ph C C Na| + L 3 H3O| (c) CH3C' C MgBr ethylene oxide (d) L '+ Br(CH2)5Br HC C_ Na|(excess) + 3 14.19 Explain why graduate student Choke Fumely, in attempting to synthesize 4,4-dimethyl-2- pentyne using the reaction of H3C C'C_ Na| with tert-butyl bromide, obtained none of the desired product. L 3 14.20 Propose a synthesis of 4,4-dimethyl-2-pentyne (the compound in Problem 14.19) from an alkyl halide and an alkyne. 14.21 Outline two different preparations of 2-pentyne that involve an alkyne and an alkyl halide. 14.22 Propose another pair of reactants that could be used to prepare 2-heptyne (the product in Eq. 14.28). 14.8 ORGANIC SYNTHESIS USING ALKYNES Let’s tie together what we’ve learned about alkyne reactions and organic synthesis. The solu- tion to Study Problem 14.2 requires all of the fundamental operations of organic synthesis: the formation of carbon–carbon bonds, the transformation of functional groups, and the establish- ment of stereochemistry (Sec.
    [Show full text]
  • S1 Supporting Information Copper-Catalyzed
    Supporting Information Copper-Catalyzed Semihydrogenation of Internal Alkynes with Molecular Hydrogen Takamichi Wakamatsu, Kazunori Nagao, Hirohisa Ohmiya*, and Masaya Sawamura* Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060-0810, Japan Table of Contents Instrumentation and Chemicals S1 Characterization Data for Alkynes S1–S2 Procedure for the Copper-Catalyzed Semihydrogenation of Alkynes S2 Characterization Data for Alkenes S3–S5 References S5 NMR Spectra S6–S31 Instrumentation and Chemicals NMR spectra were recorded on a JEOL ECX-400, operating at 400 MHz for 1H NMR and 100.5 13 1 13 MHz for C NMR. Chemical shift values for H and C are referenced to Me4Si and the residual solvent resonances, respectively. Mass spectra were obtained with Thermo Fisher Scientific Exactive, JEOL JMS-T100LP or JEOL JMS-700TZ at the Instrumental Analysis Division, Equipment Management Center, Creative Research Institution, Hokkaido University. TLC analyses were performed on commercial glass plates bearing 0.25-mm layer of Merck Silica gel 60F254. Silica gel (Kanto Chemical Co., Silica gel 60 N, spherical, neutral) was used for column chromatography. Materials were obtained from commercial suppliers or prepared according to standard procedure unless otherwise noted. CuCl was purchased from Aldrich Chemical Co., stored under nitrogen, and used as it is. NatOBu, octane and 6-dodecyne 1a were purchased from TCI Chemical Co., stored under nitrogen, and used as it is. Diphenylacetylene 1j was purchased from Wako Chemical Co., stored under nitrogen, and used as it is. 1,4-Dioxane was purchased from Kanto Chemical Co., distilled from sodium/benzophenone and stored over 4Å molecular sieves under nitrogen.
    [Show full text]
  • The Synthesis of a Polydiacetylene to Create a Novel Sensory Material
    SELDE, KRISTEN A., M.S. The Synthesis of a Polydiacetylene to Create a Novel Sensory Material. (2007) Directed by Dr. Darrell Spells. 47pp. Sensory materials that respond to chemical and mechanical stimuli are under development in many laboratories. There are many significant uses of polydiacetylene compounds as sensory material. They have been applied to drug delivery, drug design, biomolecule development, cosmetics, and national security. In this study, experiments were carried out toward the development of a novel sensory material based on the established synthetic research on polydiacetylene compounds. Synthetic routes toward sensory materials with different head groups, different carbon chains lengths, and the incorporation of molecular imprints were explored. Diacetylene moieties, which can be used for polymer vesicle formation, were prepared by two main routes. In one route, 1-iodo-1-octyne and 1-iodo-1-dodecyne were prepared as starting materials for the synthesis of two diacetylene compounds (Diacetylene I and Diacetylene II). In the other route, a mesityl alkyne was used to prepare 5-iodo-1-pentyne, which was then used to prepare a triethylamino alkyne. This in turn was used to synthesize a diacetylene (Diacetylene III). Although each diacetylene product was formed, purification by column chromatography was found to be difficult. Experiments in vesicle formation, with and without molecular imprints, were also carried out using commercially available diacetylenes . THE SYNTHESIS OF A POLYDIACETYLENE TO CREATE A NOVEL SENSORY
    [Show full text]
  • Development of a Solid-Supported Glaser-Hay Reaction and Utilization in Conjunction with Unnatural Amino Acids
    W&M ScholarWorks Dissertations, Theses, and Masters Projects Theses, Dissertations, & Master Projects 2015 Development of a Solid-Supported Glaser-Hay Reaction and Utilization in Conjunction with Unnatural Amino Acids Jessica S. Lampkowski College of William & Mary - Arts & Sciences Follow this and additional works at: https://scholarworks.wm.edu/etd Part of the Organic Chemistry Commons Recommended Citation Lampkowski, Jessica S., "Development of a Solid-Supported Glaser-Hay Reaction and Utilization in Conjunction with Unnatural Amino Acids" (2015). Dissertations, Theses, and Masters Projects. Paper 1539626985. https://dx.doi.org/doi:10.21220/s2-r9jh-9635 This Thesis is brought to you for free and open access by the Theses, Dissertations, & Master Projects at W&M ScholarWorks. It has been accepted for inclusion in Dissertations, Theses, and Masters Projects by an authorized administrator of W&M ScholarWorks. For more information, please contact [email protected]. Development of a Solid-Supported Glaser-Hay Reaction and Utilization in Conjunction with Unnatural Amino Acids Jessica Susan Lampkowski Ida, Michigan B.S. Chemistry, Siena Heights University, 2013 A Thesis presented to the Graduate Faculty of the College of William and Mary in Candidacy for the Degree of Master of Science Chemistry Department The College of William and Mary May, 2015 COMPLIANCE PAGE Research approved by Institutional Biosafety Committee Protocol number: BC-2012-09-13-8113-dyoung01 Date(s) of approval: This protocol will expire on 2015-11-02 APPROVAL PAGE This
    [Show full text]
  • Strain-Promoted 1,3-Dipolar Cycloaddition of Cycloalkynes and Organic Azides
    Top Curr Chem (Z) (2016) 374:16 DOI 10.1007/s41061-016-0016-4 REVIEW Strain-Promoted 1,3-Dipolar Cycloaddition of Cycloalkynes and Organic Azides 1 1 Jan Dommerholt • Floris P. J. T. Rutjes • Floris L. van Delft2 Received: 24 November 2015 / Accepted: 17 February 2016 / Published online: 22 March 2016 Ó The Author(s) 2016. This article is published with open access at Springerlink.com Abstract A nearly forgotten reaction discovered more than 60 years ago—the cycloaddition of a cyclic alkyne and an organic azide, leading to an aromatic triazole—enjoys a remarkable popularity. Originally discovered out of pure chemical curiosity, and dusted off early this century as an efficient and clean bio- conjugation tool, the usefulness of cyclooctyne–azide cycloaddition is now adopted in a wide range of fields of chemical science and beyond. Its ease of operation, broad solvent compatibility, 100 % atom efficiency, and the high stability of the resulting triazole product, just to name a few aspects, have catapulted this so-called strain-promoted azide–alkyne cycloaddition (SPAAC) right into the top-shelf of the toolbox of chemical biologists, material scientists, biotechnologists, medicinal chemists, and more. In this chapter, a brief historic overview of cycloalkynes is provided first, along with the main synthetic strategies to prepare cycloalkynes and their chemical reactivities. Core aspects of the strain-promoted reaction of cycloalkynes with azides are covered, as well as tools to achieve further reaction acceleration by means of modulation of cycloalkyne structure, nature of azide, and choice of solvent. Keywords Strain-promoted cycloaddition Á Cyclooctyne Á BCN Á DIBAC Á Azide This article is part of the Topical Collection ‘‘Cycloadditions in Bioorthogonal Chemistry’’; edited by Milan Vrabel, Thomas Carell & Floris P.
    [Show full text]
  • A. Discovery of Novel Reactivity Under the Sonogashira Reaction Conditions B. Synthesis of Functionalized Bodipys and BODIPY-Sug
    A. Discovery of novel reactivity under the Sonogashira reaction conditions B. Synthesis of functionalized BODIPYs and BODIPY-sugar conjugates Ravi Shekar Yalagala, M.Phil Department of Chemistry Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy Faculty of Mathematics and Science, Brock University St. Catharines, Ontario © 2016 ABSTRACT A. During our attempts to synthesize substituted enediynes, coupling reactions between terminal alkynes and 1,2-cis-dihaloalkenes under the Sonogashira reaction conditions failed to give the corresponding substituted enediynes. Under these conditions, terminal alkynes underwent self-trimerization or tetramerization. In an alternative approach to access substituted enediynes, treatment of alkynes with trisubstituted (Z)- bromoalkenyl-pinacolboronates under Sonogashira coupling conditions was found to give 1,2,4,6-tetrasubstituted benzenes instead of Sonogashira coupled product. The reaction conditions and substrate scopes for these two new reactions were investigated. B. BODIPY core was functionalized with various functional groups such as nitromethyl, nitro, hydroxymethyl, carboxaldehyde by treating 4,4-difluoro-1,3,5,7,8- pentamethyl-2,6-diethyl-4-bora-3a,4a-diaza-s-indacene with copper (II) nitrate trihydrate under different conditions. Further, BODIPY derivatives with alkyne and azido functional groups were synthesized and conjugated to various glycosides by the Click reaction under the microwave conditions. One of the BODIPY–glycan conjugate was found to form liposome upon rehydration. The photochemical properties of BODIPY in these liposomes were characterized by fluorescent confocal microscopy. ii ACKNOWLEDGEMENTS I am extremely grateful to a number of people. Without their help, this document would have never been completed. First and foremost, I would like to thank my supervisor and mentor Professor Tony Yan for his guidance and supervision to make the thesis possible.
    [Show full text]
  • Indolizidines and Quinolizidines: Natural Products and Beyond
    Indolizidines and quinolizidines: natural products and beyond Edited by Joseph Philip Michael Generated on 05 October 2021, 08:24 Imprint Beilstein Journal of Organic Chemistry www.bjoc.org ISSN 1860-5397 Email: [email protected] The Beilstein Journal of Organic Chemistry is published by the Beilstein-Institut zur Förderung der Chemischen Wissenschaften. This thematic issue, published in the Beilstein Beilstein-Institut zur Förderung der Journal of Organic Chemistry, is copyright the Chemischen Wissenschaften Beilstein-Institut zur Förderung der Chemischen Trakehner Straße 7–9 Wissenschaften. The copyright of the individual 60487 Frankfurt am Main articles in this document is the property of their Germany respective authors, subject to a Creative www.beilstein-institut.de Commons Attribution (CC-BY) license. Indolizidines and quinolizidines: natural products and beyond Joseph P. Michael Editorial Open Access Address: Beilstein Journal of Organic Chemistry 2007, 3, No. 27. Molecular Sciences Institute, School of Chemistry, University of the doi:10.1186/1860-5397-3-27 Witwatersrand, PO Wits 2050, South Africa Received: 24 September 2007 Email: Accepted: 26 September 2007 Joseph P. Michael - [email protected] Published: 26 September 2007 © 2007 Michael; licensee Beilstein-Institut. License and terms: see end of document. Alkaloids occur in such astonishing profusion in nature that amphibians. [5,6] It is thus hardly surprising that both the struc- one tends to forget that they are assembled from a relatively tural elucidation and the total synthesis of these and related small number of structural motifs. Among the motifs that are alkaloids continue to attract the attention of eminent chemists, most frequently encountered are bicyclic systems containing as borne out by the seemingly inexhaustible flow of publica- bridgehead nitrogen, especially 1-azabicyclo[4.3.0]nonanes and tions in prominent journals.
    [Show full text]
  • 4-(Phenylsulfonyl) Butanoic Acid: Preparation, Dianion Generation
    Loyola University Chicago Loyola eCommons Dissertations Theses and Dissertations 1990 4-(Phenylsulfonyl) Butanoic Acid: Preparation, Dianion Generation, and Application to Four Carbon Chain Extension ; Studies of Organophosphorus Compounds Derived from Serine Jeffrey A. Frick Loyola University Chicago Follow this and additional works at: https://ecommons.luc.edu/luc_diss Part of the Chemistry Commons Recommended Citation Frick, Jeffrey A., "4-(Phenylsulfonyl) Butanoic Acid: Preparation, Dianion Generation, and Application to Four Carbon Chain Extension ; Studies of Organophosphorus Compounds Derived from Serine" (1990). Dissertations. 3163. https://ecommons.luc.edu/luc_diss/3163 This Dissertation is brought to you for free and open access by the Theses and Dissertations at Loyola eCommons. It has been accepted for inclusion in Dissertations by an authorized administrator of Loyola eCommons. For more information, please contact [email protected]. This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License. Copyright © 1990 Jeffrey A. Frick I. 4-(PHENYLSULFONYL)BUTANOIC ACID. PREPARATION, DIANION GENERATION, AND APPLICATION TO FOUR CARBON CHAIN EXTENSION II. STUDIES OF ORGANOPHOSPHORUS COMPOUNDS DERIVED FROM SERINE by Jeffrey A. Frick A Dissertation Submitted to the Faculty of the Graduate School of Loyola University of Chicago in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy June 1990 ACKNOWLEDGMENTS The author wishes to express his deepest thanks to Dr. Charles Thompson for his enthusiasm, his support, and his friendship; all of which made this work possible. Thanks are expressed to the members of the Dissertation Committee: Dr. Albert Herlinger, Dr. Kenneth Olsen, Prof. James Babler, and Prof. John Cashman, for their willingness to serve in this capacity.
    [Show full text]
  • Gfsorganics & Fragrances
    Chemicals for Flavors GFSOrganics & Fragrances GFS offers a broad range of specialty organic chemicals Specialized chemistries we as building blocks and intermediates for the manufacture of offer include: flavors and fragrances. • Alkynes Over 5,500 materials, including 1,400 chemicals from natural sources, are used for flavor • Alkynols enhancements and aroma profiles. These aroma chemicals are integral components of • Olefins the continued growth within consumer products and packaged foods. The diversity of products can be attributed to the broad spectrum of organic compounds derived from • Unsaturated Acids esters, aldehydes, lactones, alcohols and several other functional groups. • Unsaturated Esters • DIPPN and other Products GFS Chemicals manufactures a wide range of organic intermediates that have been utilized in a multitude of personal care applications. For example, we support Why GFS? several market leading companies in the manufacture and supply of alkyne based aroma chemicals. • Specialized Chemistries • Tailored Specifications As such, we understand the demanding nature of this fast changing market and are fully • From Grams to Metric Tons equipped to overcome process challenges and manufacture the novel chemical products • Responsive Technical Staff that you need, when you need them. We offer flexible custom manufacturing services to produce high purity products with the assurance of quality and full confidentiality. • Uncompromised Product Quality Our state-of-the-art manufacturing facility, located in Columbus, OH is ISO 9001:2008 certified. As a U.S. based manufacturer we have a proven record of helping you take products from development to commercialization. Our technical sales experts are readily accessible to discuss your project needs and unique product specifications.
    [Show full text]
  • Développement De Réactions D'hydratation D'alcynes Possédant Un Groupement Fluoré À La Position Propargylique Catalysées À L'or
    Développement de réactions d'hydratation d'alcynes possédant un groupement fluoré à la position propargylique catalysées à l'or Mémoire Mélissa Cloutier Maîtrise en chimie - avec mémoire Maître ès sciences (M. Sc.) Québec, Canada © Mélissa Cloutier, 2019 Développement de réactions d’hydratation d’alcynes possédant un groupement fluoré à la position propargylique catalysées à l’or Mémoire Mélissa Cloutier Sous la direction de : Jean-François Paquin Résumé La catalyse à l’or a retenu l’attention ces dernières années à cause de la capacité de cet atome d’activer les alcynes en vue d’une attaque nucléophile, dans des conditions douces, en présence d’autres groupements fonctionnels. Des effets relativistes seraient à l’origine de certaines propriétés uniques de l’or. Si le produit de Markovnikov est généralement obtenu lorsque la réaction d’addition est effectuée sur des alcynes terminaux, l’utilisation d’alcynes internes mène à la formation de régioisomères. Ce problème de régiosélectivité peut être, complètement ou partiellement, résolu en utilisant, entre autres, des groupements électroattracteurs à l’une des positions propargyliques. Dans le cadre de ses travaux, la réactivité de substrats portant un groupement fluoré en position propargylique a été explorée. Ici, l’attaque nucléophile se fera de manière préférentielle au carbone de l’alcyne distal du groupement fluoré, faisant office de groupement électroattracteur. Le premier projet porte sur la réaction d’hydratation d’alcynes trifluorométhylés et pentafluorosulfanylés catalysée à l’or pour la formation de cétone α-CF3 et α-SF5, respectivement. Les groupements fluorés, étant électroattracteurs, jouent le rôle du groupement directeur pour ces transformations et mènent à l’obtention d’un seul régioisomère.
    [Show full text]
  • Chemical in Baobab (Adansonia Digitata) from Sudan
    Vol. 14(21), pp. 907-914, 23 May, 2019 DOI: 10.5897/AJAR2019.13862 Article Number: 83F45A861057 ISSN: 1991-637X Copyright ©2019 African Journal of Agricultural Author(s) retain the copyright of this article http://www.academicjournals.org/AJAR Research Full Length Research Paper Identification of 1-decyne as a new volatile allele- chemical in baobab (Adansonia digitata) from Sudan Hala Sad Alla Maliek Elmadni1,2, Maryia Mishyna1,3 and Yoshiharu Fujii1,2* 1Department of International Environmental and Agricultural Science, Faculty of Agriculture, Tokyo University of Agriculture and Technology, 183-8509 Tokyo, Japan. 2Department of General Administration of technology Transfer and Extension, Federal Ministry of Agriculture and Forest, 461 Khartoum, Sudan. 3School of Food Science and Bioengineering, Zhejiang Gongshang University, Hangzhou, China. Received 3 January, 2019; Accepted 19 April, 2019 Leaf, fruit, wood, and gum of fifty-five plants collected in Sudan were evaluated by Dish pack method for their allelopathic activity through volatile chemicals using lettuce (Lactuca sativa) as a receptor plant. Several potential plants with high allelopathic activity, such as Terminalia brownie, Euphorbia hirta, Diospyros mespiliformis, Corchorus olitorius, Adansonia digitata, Hibiscus sabdariffa, were determined. Baobab (A. digitata) leaves demonstrated relatively higher inhibition (23.9 and 21.5% of hypocotyl and radicle, respectively) than most of the screened plant species. Identification of the volatile compounds using headspace gas chromatography-mass spectrometry revealed 1-decyne as the main volatile compound naturally released from dried baobab leaves. EC50 (50% growth inhibition) of radicle and hypocotyl growth of lettuce seedlings by authentic 1-decyne was determined in the headspace air using by GC-MS with Cotton Swab method at the concentration of 0.5 ng/ml.
    [Show full text]
  • Highly Accelerated Inverse Electron-Demand Cycloaddition of Electron-Deficient Azides with Aliphatic Cyclooctynes
    ARTICLE Received 22 Jul 2014 | Accepted 25 Sep 2014 | Published 10 Nov 2014 DOI: 10.1038/ncomms6378 Highly accelerated inverse electron-demand cycloaddition of electron-deficient azides with aliphatic cyclooctynes Jan Dommerholt1, Olivia van Rooijen2, Annika Borrmann1,Ce´lia Fonseca Guerra2, F. Matthias Bickelhaupt1,2 & Floris L. van Delft1 Strain-promoted azide–alkyne cycloaddition (SPAAC) as a conjugation tool has found broad application in material sciences, chemical biology and even in vivo use. However, despite tremendous effort, SPAAC remains fairly slow (0.2–0.5 M À 1 s À 1) and efforts to increase reaction rates by tailoring of cyclooctyne structure have suffered from a poor trade-off between cyclooctyne reactivity and stability. We here wish to report tremendous acceleration of strain-promoted cycloaddition of an aliphatic cyclooctyne (bicyclo[6.1.0]non-4-yne, BCN) with electron-deficient aryl azides, with reaction rate constants reaching 2.0–2.9 M À 1 s À 1. A remarkable difference in rate constants of aliphatic cyclooctynes versus benzoannulated cyclooctynes is noted, enabling a next level of orthogonality by a judicious choice of azide– cyclooctyne combinations, which is inter alia applied in one-pot three-component protein labelling. The pivotal role of azide electronegativity is explained by density-functional theory calculations and electronic-structure analyses, which indicates an inverse electron-demand mechanism is operative with an aliphatic cyclooctyne. 1 Institute for Molecules and Materials, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands. 2 Department of Theoretical Chemistry and Amsterdam Center for Multiscale Modeling, VU University Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands.
    [Show full text]