DOCSLIB.ORG

Impact of Suppression of Ethylene Action Or Biosynthesis on Flavor Metabolites in Apple (Malus Domestica Borkh) Fruits

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Impact of Suppression of Ethylene Action Or Biosynthesis on Flavor Metabolites in Apple (Malus Domestica Borkh) Fruits 5694 J. Agric. Food Chem. 2004, 52, 5694−5701 Impact of Suppression of Ethylene Action or Biosynthesis on Flavor Metabolites in Apple (Malus domestica Borkh) Fruits BRUNO G. DEFILIPPI,† ABHAYA M. DANDEKAR,‡ AND ADEL A. KADER*,‡ Department of Pomology, University of California, Davis, California 95616, and Institute for Agricultural Research (INIA), La Platina Experimental Station, Casilla 439/3, Santiago, Chile To understand the role of ethylene in regulating the overall flavor of apple fruits, ethylene production or action was reduced using transgenic apple trees suppressed for ACC-synthase or ACC-oxidase enzyme activity or by the addition of 1-methylcyclopropene (1-MCP), an ethylene action inhibitor. Flavor components were differentially regulated in response to the suppression of both ethylene biosynthesis and action. Headspace analysis of aroma production, an ethylene-associated event, showed a reduction in ester and alcohol production in the ethylene-suppressed lines and in the apples treated with 1 µLL-1 1-MCP for 20 h at 20 °C. However, no major differences were observed in the concentrations of aldehyde volatiles. Other flavor metabolites that showed an ethylene-dependent pattern were organic acids and sugars. Malic acid degradation was significantly reduced under ethylene-suppressed conditions, showing a recovery after the fruit was exposed to ethylene. Sucrose and fructose concentrations were influenced by suppression or enhancement of ethylene. Total phenolics as well as individual phenolic compounds showed an ethylene-dependent regulation only in response to the suppression of ethylene biosynthesis, but not when ethylene action was inhibited. KEYWORDS: Aroma; fruit flavor complex; phenolic compounds; sugars; Malus domestica; organic acids; transgenic apple fruit INTRODUCTION contribution of sorbitol in apple (2, 6). Sugars are transported Among the many quality parameters defining the desirability from source organs and accumulate in fruit during their of fruits and vegetables, there are important nonvisual charac- development, where they form starch. The hydrolysis of starch teristics such as texture, nutritional value, and flavor, which in the fruit is an important source of sugars in the last stages of influence the final acceptance by the consumer (1). Flavor fruit development and starts before the climacteric peak (6). composition has been defined as a complex attribute of quality, The effect of ethylene on sugar accumulation has been studied in which the mix of sugars, acids, and volatiles plays a primary mainly using TSS as an indicator of sweetness, and it has been role (2). Another interesting group of metabolites are phenolic observed that the suppression of ethylene action or biosynthesis compounds, which are important secondary metabolites con- does not alter TSS accumulation during ripening; therefore, it tributing to overall fruit quality, including flavor, nutritional is considered an ethylene-independent event (7, 8). However, value, and appearance (3). what remains unclear is the behavior of individual sugars in During fruit development there are many changes in flavor response to ethylene regulation. metabolites caused by their synthesis, transport, or degradation. Regarding acidity, malic acid is the most abundant organic In climacteric fruits, ethylene plays an important role as a acid in apples, followed distantly by citric acid (6, 9). Because modulator of ripening. All of these fruit quality related organic acids are substrates of respiration, their levels typically metabolites may be directly regulated by ethylene (ethylene- decrease during ripening. The use of inhibitors of ethylene dependent processes) or by other signals (ethylene-independent biosynthesis and action have shown a reduction in the loss of process) (4). acidity during ripening, which suggests that organic acids In addition to the flavor metabolites mentioned above, sugars metabolism is an ethylene-dependent process (7). and organic acids measured through total soluble solids (TSS) In flavor, phenolic compounds are major substances respon- and titratable acidity (TA), respectively, are most commonly sible of bitterness and astringency, in which tannins, catechins, associated with fruit taste (5). The sugars sucrose, glucose, and and epicatechins have been identified as astringent molecules fructose are responsible for the sweetness, with some minor (10). On the other hand, during enzymatic browning in which there is a development of undesirable colors and flavors, * Corresponding author [telephone (530) 752-0909; fax (530) 752-8502; catechins and chlorogenic acid are the main substrates for the e-mail [email protected]]. † Institute for Agricultural Research and University of California-Davis. reaction (11). In general, there is a reduction in the total phe- ‡ University of California, Davis. nolic composition through apple fruit development; however, 10.1021/jf049504x CCC: $27.50 © 2004 American Chemical Society Published on Web 08/17/2004 Flavor Metabolites in Apple J. Agric. Food Chem., Vol. 52, No. 18, 2004 5695 this behavior during maturation and storage varies according solution was made up to 50 mL with 80% ethanol. Then, an aliquot of to cultural conditions, cultivar (12), environmental factors (1), 10 mL was taken and dried under a nitrogen stream at 50 °C. The and physiological stage at harvest (13). The evidence for the residue was dissolved in 2 mL of 0.2 N H2SO4 with 0.05% EDTA. relationship between ethylene and phenolic composition in fruits The sample was loaded onto an activated Sep-Pak C18 cartridge and is derived from the effect of storage conditions on ethylene the eluate collected. The sample was washed through with a further 4 mL of the solution. The eluate was filtered through a 0.45 µm filter biosynthesis and action, including low temperatures, low oxygen and analyzed by HPLC (Hewlett-Packard model 1050 pump) connected concentration, and high carbon dioxide concentration (3, 13, to a photodiode array detector (HP model 1040M series II) with an 14). In general, results indicate that phenolic metabolism in apple autosampler (HP model 1050), operated by HP ChemStation software is stable under these conditions, and few changes are significant, (Hewlett-Packard, Menlo Park, CA). In this case, a refractive index suggesting that phenolic metabolism and turnover are low during (RI) monitor (model 1750; Bio-Rad Laboratories Inc., Hercules, CA) long-term storage. was connected in series with the DAD. Sugars and organic acids were In addition to the four basic flavors (sweet, sour, salty, and separated by a stainless steel ION-300 column (300 mm × 7.8 mm, bitter) that humans can recognize in fruits and vegetables, aroma 10 µm) (Interaction Chromatography, San Jose, CA) using 0.0085 N -1 has an important influence on the final consumer acceptance H2SO4 at a flow rate of 0.4 mL min . Detection was at 210 nm for of the commodity (15). Fruit aroma is determined by a complex organic acids and at 250 nm for sugars using the RI detector. Total Phenolics. Total phenolic compounds were quantified by using mixture of a large number of volatile compounds including the Folin-Ciocalteu spectrophotometric method (22). Data are reported alcohols, aldehydes, carboxylic esters, and ketones (16). Esters as milligrams of p-coumaric acid/100 mL of juice. Because differences are among the most important classes of volatiles in apple fruit in phenolic composition have been determined among fruit tissues (13), flavor, with more than 20 esters that have been detected in apple 5 g samples were taken containing either 20% of peel or no peel. cultivars (17, 18). In apple, the typical flavor develops during Individual Phenolic Compounds. Individual phenolics were identi- ripening with a maximum endogenous ester concentration fied according to the procedure of Gil et al. (23). After extraction of 5 occurring at the climacteric peak (16, 18, 19). In this paper we g of frozen tissue with methanol, juice was then filtered through a 0.45 demonstrate that aroma production is under ethylene regulation µm filter for analysis by HPLC. Separations were carried out using using both biotechnological and chemical approaches for the system described above. A reverse phase C18 Nucleosil column × ) suppressing ethylene biosynthesis or action. (150 4.6 mm, particle size 5 µm), with a guard column of the same material (MetaChem Technologies Inc., Torrance, CA) was used. Acetic acid (2.5%) was added to water and methanol to increase peak MATERIALS AND METHODS resolutions before preparation of the following mobile phases: water Plant Material and Treatments. Transgenic Greensleeves apple (A); 88% water + 12% methanol (B); 20% water + 80% methanol fruits suppressed for ethylene biosynthesis were obtained from different (C); and methanol (D). Elution started with 100% A, which remained lines grown in an experimental orchard in northern California. The lines isocratic until 5 min. A gradient was then used to reach 100% B at 10 used in these experiments were transformed using binary vectors that min, holding it isocratic for an additional 3 min. From 13 to 35 min a express the cDNAs corresponding to ACC-synthase (ACS) and ACC- linear gradient was used to reach 50% B and 50% C and then 100% C oxidase (ACO) enzymes in either a sense or antisense pattern (20). at 40 min. The column was then washed with 100% D at 42 min. The - Fruits of selected Greensleeves apple lines including a nontransformed flow rate was 1 mL min 1, and chromatograms were recorded at 510,
Load more

Recommended publications
  • Esters Introduction Structurally, an Ester Is a Compound That Has an Alkoxy (OR) Group Attached to the Carbonyl Group
    Esters Introduction Structurally, an ester is a compound that has an alkoxy (OR) group attached to the carbonyl group. O R C O R' R may be H, alkyl or aryl, while R’ may be alkyl or aryl only. Esters are widespread in nature. Many of the fragrances of flowers and fruits are due to the esters present. Ethyl butanoate is the chief component that accounts for the pineapple-like aroma and flavour of pineapples. 1:18 PM 1 Nomenclature of Esters Names of esters consist of two words that reflect the composite structure of the ester. The first word is derived from the alkyl group of the alcohol component, and the second word from the carboxylate group of the carboxylic acid component of the ester. The name of the carboxylate portion is derived by substituting the -ic acid suffix of the parent carboxylic acid with the –ate suffix. The alkyl group is cited first followed by the carboxylate group separated by a space. An ester is thus named as an alkyl 1:18 PM alkanoate. 2 IUPAC Nomenclature of Esters Examples 1:18 PM 3 Synthesis of Esters Preparative Strategies Highlighted below are some of the most common strategies by which esters are prepared. The esters are commonly prepared from the reaction of carboxylic acids, acid chlorides and acid anhydrides with alcohols. 1:18 PM 4 Synthesis of Esters Acid-Catalysed Esterification of a Carboxylic Acid and an Alcohol The acid-catalysed reaction of carboxylic acids and alcohols provides esters. Typically, a catalytic amount of a strong inorganic (mineral) acid such as H2SO4, HCl and H3PO4 is used.
    [Show full text]
  • Fermentation and Ester Taints
    Fermentation and Ester Taints Anita Oberholster Introduction: Aroma Compounds • Grape‐derived –provide varietal distinction • Yeast and fermentation‐derived – Esters – Higher alcohols – Carbonyls – Volatile acids – Volatile phenols – Sulfur compounds What is and Esters? • Volatile molecule • Characteristic fruity and floral aromas • Esters are formed when an alcohol and acid react with each other • Few esters formed in grapes • Esters in wine ‐ two origins: – Enzymatic esterification during fermentation – Chemical esterification during long‐term storage Ester Formation • Esters can by formed enzymatically by both the plant and microbes • Microbes – Yeast (Non‐Saccharomyces and Saccharomyces yeast) – Lactic acid bacteria – Acetic acid bacteria • But mainly produced by yeast (through lipid and acetyl‐CoA metabolism) Ester Formation Alcohol function Keto acid‐Coenzyme A Ester Ester Classes • Two main groups – Ethyl esters – Acetate esters • Ethyl esters = EtOH + acid • Acetate esters = acetate (derivative of acetic acid) + EtOH or complex alcohol from amino acid metabolism Ester Classes • Acetate esters – Ethyl acetate (solvent‐like aroma) – Isoamyl acetate (banana aroma) – Isobutyl acetate (fruit aroma) – Phenyl ethyl acetate (roses, honey) • Ethyl esters – Ethyl hexanoate (aniseed, apple‐like) – Ethyl octanoate (sour apple aroma) Acetate Ester Formation • 2 Main factors influence acetate ester formation – Concentration of two substrates acetyl‐CoA and fusel alcohol – Activity of enzyme responsible for formation and break down reactions • Enzyme activity influenced by fermentation variables – Yeast – Composition of fermentation medium – Fermentation conditions Acetate/Ethyl Ester Formation – Fermentation composition and conditions • Total sugar content and optimal N2 amount pos. influence • Amount of unsaturated fatty acids and O2 neg. influence • Ethyl ester formation – 1 Main factor • Conc. of precursors – Enzyme activity smaller role • Higher fermentation temp formation • C and N increase small effect Saerens et al.
    [Show full text]
  • Ketone Ester Effects on Metabolism and Transcription
    Ketone Ester Effects On Metabolism And Transcription Is Ave bookish or randie after spherulitic Wilfrid pasquinades so nocuously? Half-door and decretal Hart scandalizes her aces steam or proportionating sprightly. Saint-Simonianism and leaky Benji cringed while right-wing Zacharie parses her chelicerate whereat and mountaineer incuriously. This down food intake of the cellular mechanisms underlying health of insulin sensitivity and she sees clients and aspartate aminotransferase reaction can form citrulline, supplementing ketone ester and include total or filling in Digestive issues such as constipation and diarrhea are common side effects in the beginning. This common chemistry allows cells to use a small set of metabolic intermediates to carry chemical groups between different reactions. Practical considerations in the use of stable isotope labelled compounds as tracers in clinical studies. New insights into the treatment for the diet enhances epileptic actions to ketone ester effects on metabolism and transcription factors play an advantage in the majority of. What are the symptoms of ketosis and ketoacidosis? In this case, fat and carb but it could be from very poor quality of food. And it has to get burned, what are we looking at right here? Carbohydrates for training and competition. One that is vulnerable is cysteine. Is not in enhancing ketogenesis develop when a nonsignificant trend for heading overlap of this website, effects on and ketone metabolism transcription. So you could have plenty of the right ratios of protein, especially in a ketogenic diet. Ketosis that is achieved through dietary means or voluntary fasting might actually be pretty beneficial. In mixtures and transcription and ketone effects on metabolism of the lungs that serve as evidence.
    [Show full text]
  • Bio Isolation, Chemical Purification, Identification, Antimicrobial And
    International Journal of Molecular Biology: Open Access Research Article Open Access Bio-guided isolation, chemical purification, identification, antimicrobial and synergistic efficacy of extracted essential oils from stem bark extract of Spondias mombin (Linn). Abstract Volume 4 Issue 4 - 2019 The purpose of this research work is to bio-guided isolate, purify, chemical identification, antimicrobial and Synergistic efficacy of extracted essential oils from ethyl acetate extract Oludare Temitope Osuntokun,1 Gamberini of Spondias mombin. The ethyl acetate stem bark extract of Spondias mombin were air- M Cristina2 dried, chopped into smaller pieces and cold extracted exhaustively with ethylacetate. The 1Department of Microbiology, Faculty of Science, Adekunle crude extract was partitioned using various solvents and the dichloromethane fraction was Ajasin University, Nigeria concentrated and fractionated using column chromatography packed with Silica gel and 2Department of Life Sciences, University of Modena and Reggio Sephadex-LH and eluted with appropriate solvent systems accordingly. In order to obtain Emilia, Italy pure extracts, partially purified fractions were further purified. The structures of the isolated compounds were determined by using data obtained from GC-MS spectrum. The compound Correspondence: Oludare Temitope Osuntokun, Department isolated includeAspidofractinine-3-methanol, Phthalic acid, 2-ethylhexyl tetradecyl of Microbiology, Faculty of Science, Adekunle Ajasin University, ester, Phthalic acid, di (2-propylpentyl) ester), (9-(2’, 2’-Dimethylpropanoilhydrazono)- Akungba-Akoko, Ondo state, Nigeria, 3,6-dichloro-2,7-bis-[2-(diethylamino)-ethoxy]fluorine) and Tere phthalic acid, dodecyl Email 2-ethylhexyl ester.These compounds have individual and synergistic activity against Gram Received: August 08, 2019 | Published: August 26, 2019 negative (E.coli), Gram-positive (Bacillus subtilis) and (Aspergillusflavus) at 10, 5, 2.5 and 1.25 g/mL.
    [Show full text]
  • Correlation and Prediction of Mixing Thermodynamic Properties of Ester-Containing Systems: Ester+Alkane and Ester+Ester Binary S
    J. Chem. Thermodynamics 54 (2012) 41–48 Contents lists available at SciVerse ScienceDirect J. Chem. Thermodynamics journal homepage: www.elsevier.com/locate/jct Correlation and prediction of mixing thermodynamic properties of ester-containing systems: Ester + alkane and ester + ester binary systems and the ternary dodecane + ethyl pentanoate + ethyl ethanoate ⇑ Noelia Pérez a, Luís Fernández a, Juan Ortega a, , Francisco J. Toledo a, Jaime Wisniak b a Laboratorio de Termodinámica y Fisicoquímica de Fluidos, Parque Científico-Tecnológico, Universidad de Las Palmas de Gran Canaria, Canary Islands, Spain b Deparment of Chemical Engineering, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel article info abstract Article history: E E Excess thermodynamic properties V m and Hm, have been measured for the ternary mixture dodecane + Received 25 December 2011 ethyl pentanoate + ethyl ethanoate and for the corresponding binaries dodecane + ethyl pentanoate, Received in revised form 7 March 2012 dodecane + ethyl ethanoate, ethyl pentanoate + ethyl ethanoate at 298.15 K. All mixtures show Accepted 9 March 2012 endothermic and expansive effects. Experimental results are correlated with a suitable equation whose Available online 20 March 2012 final form for the excess ternary quantity ME contains the particular contributions of the three binaries (i–j) and a last term corresponding to the ternary, all of them obtained considering fourth-order interac- Keywords: tions. The fit goodness for all mixtures is good and comparable to others equations taken from the liter- Excess molar enthalpies ature. In this work the dissolution model for the binaries and ternary is analyzed with a special attention Excess molar volumes Ternary mixture to ester–ester binaries whose behaviour is discussed.
    [Show full text]
  • One-Step Synthesis of Ester from Alkene
    ー論文ー ●One-step synthesis of ester from alkene Madoka Furuta M.C.Kung and H.H.Kung UFO Project Northwestern University Abstract A one-step synthesis of ethylacetate from a feed mixture of ethene, oxygen, and water using a supported Pd and silicotungstic acid catalyst was demonstrated. At about 180℃ and 25% ethene conversion, ethylacetate could be produced with to 46% selectivity, with 34% acetic acid and ethanol that could be recycled. The catalyst was believed to be bifunctional, with Pd providing the oxidation function and the silicotungstic acid providing the acidic function. And this catalyst system had an activity that could produce isopropylacrylate from a feed mixture of propene, oxygen, and water. 1 Introduction C2H5OH + O2 = CH3COOH + H2O (2) Carboxylic acid esters are used in a wide range of applications. They are used, for example, as plasticizers, solvents, surface-active Finally, ethyl acetate is produced by the esterification of ethanol agents, and flavor and perfume materials. There are many known with acetic acid over a catalyst. methods to produce esters. The most common method is the C2H5OH + CH3COOH = CH3COOC2H5 + H2O (3) esterification, which is a reaction of alcohol with carboxylic acid1,2）. For example, ethyl acrylate is synthesized from ethyl alcohol and Thus the overall reaction is acrylic acid, and ethyl acetate from ethyl alcohol and acetic acid. An 2C2H4 + O2 = CH3COOC2H5 (4) acidic catalyst, which can be a mineral acid, or polymeric material containing chemically-bound acid groups, such as sulfonated Such a one-step process has the advantage of starting with reactants, polystyrene, is commonly used in the esterification.
    [Show full text]
  • Notices of Commencement Received File:///W:/Oneepa/Newchems/Pubs/5D2-IMD/NOC-03-21.Html
    Notices of Commencement Received file:///W:/OneEPA/Newchems/pubs/5d2-IMD/NOC-03-21.html If Received Commencement amendment, Case No. Chemical Substance Date Date type of amendment (G) Biofuel producing Saccharomyces cerevisiae mo J-18-0002 06/28/2019 06/19/2018 N genetically stable (G) Biofuel producing Saccharomyces cerevisiae mo J-18-0003 06/28/2019 06/24/2018 N genetically stable J-19-0011 06/03/2019 06/02/2019 N (G) Genetically modified microorganism (S) 2-Propenoic acid, 2-methyl-, polymer with butyl 2-propenoate, 2-hydroxyethyl 2-methyl-2-propenoat P-01-0767 06/10/2019 05/03/2019 N (hydroxymethyl)-2-propenamide, 2-methyl-2-propen and 2-propenenitrile, ammonium salt (S) Isocyanic acid, polymethylenepolyphenylene este P-11-0080 06/07/2019 05/22/2019 N polymer with 1,2-propanediol, 2-(2-butoxyethoxy)et and n,n-dibutyl-2-hydroxyacetamide-blocked (S) Isocyanic acid, polymethylenepolyphenylene este P-14-0742 06/13/2019 05/26/2019 N polymer with 1,2-propanediol, 2-(2-butoxyethoxy)et and n,n-dibutyl-2-hydroxyacetamide-blocked P-16-0375 06/10/2019 03/17/2019 N (G) Alkyl methacrylates, polymer with olefines P-16-0400 06/18/2019 06/03/2019 N (S) Alkanes, C11-16, branched and linear Revised generic P-16-0532A 06/20/2019 04/17/2019 (G) Oxo heteromonocycle chemical name (G) Poly(alkyl-oxo-2-propen-1-yl)ester with alkanea P-17-0152 06/28/2019 06/04/2019 N trialkyl chloride and alkoxy-poly(oxy-alkanediyl) (G) Alkylaminium-trialkyl-2-[(2-methyl-1-oxo-2-pro 1-yl)oxy]-, halide (1:1), polymer with alpha-(2-meth P-17-0152 06/28/2019 06/04/2019 N 1-oxo-2-propen-1-yl)-
    [Show full text]
  • Ester Synthesis Lab (Student Handout)
    Name: ________________________ Lab Partner: ____________________ Date: __________________________ Class Period: ____________________ Ester Synthesis Lab (Student Handout) Lab Report Components: The following must be included in your lab book in order to receive full credit. 1. Purpose 2. Hypothesis 3. Procedure 4. Observation/Data Table 5. Results 6. Mechanism (In class) 7. Conclusion Introduction The compounds you will be making are also naturally occurring compounds; the chemical structure of these compounds is already known from other investigations. Esters are organic molecules of the general form: where R1 and R2 are any carbon chain. Esters are unique in that they often have strong, pleasant odors. As such, they are often used in fragrances, and many artificial flavorings are in fact esters. Esters are produced by the reaction between alcohols and carboxylic acids. For example, reacting ethanol with acetic acid to give ethyl acetate is shown below. + → + In the case of ethyl acetate, R1 is a CH3 group and R2 is a CH3CH2 group. Naming esters systematically requires naming the functional groups on both sides of the bridging oxygen. In the example above, the right side of the ester as shown is a CH3CH2 1 group, or ethyl group. The left side is CH3C=O, or acetate. The name of the ester is therefore ethyl acetate. Deriving the names of the side from the carboxylic acid merely requires replacing the suffix –ic with –ate. Materials • Alcohol • Carboxylic Acid o 1 o A o 2 o B o 3 o C o 4 Observation Parameters: • Record the combination of carboxylic acid and alcohol • Observe each reactant • Observe each product Procedure 1.
    [Show full text]
  • In This Handout, All of Our Functional Groups Are Presented As Condensed Line Formulas, 2D and 3D Formulas and with Nomenclature Prefixes and Suffixes (If Present)
    In this handout, all of our functional groups are presented as condensed line formulas, 2D and 3D formulas and with nomenclature prefixes and suffixes (if present). Organic names are built on a foundation of alkanes, alkenes and alkynes. Those examples are presented first and you need to know those rules. The strategies can be found in Chapter 4 of our textbook (alkanes: pages 93-98, cycloalkanes 102-104, alkenes: pages 104-110, alkynes: pages 112-113 and combinations of all of them 113-115). After introducing examples of alkanes, alkenes, alkynes and combinations of them, the functional groups are presented in order of priority. A few nomenclature examples are provided for each of the functional groups. Examples of the various functional groups are presented on pages 115-135 in the textbook. Two overview pages are on pages 136-137. Some functional groups have a suffix name when they are the highest priority functional group and a prefix name when they are not the highest priority group, and these are added to the skeletal names with identifying numbers and stereochemistry terms (E and Z for alkenes, R and S for chiral centers and cis and trans for rings). Several low priority functional groups only have a prefix name. A few additional special patterns are shown on pages 98-102. The only way to learn this topic is practice (over and over). The best practice approach is to actually write out the names (on an extra piece of paper or on a white board, and then do it again). The same functional groups are used throughout the entire course.
    [Show full text]
  • Reactions of Alkenes Since  Bonds Are Stronger Than  Bonds, Double Bonds Tend to React to Convert the Double Bond Into  Bonds
    Reactions of Alkenes Since bonds are stronger than bonds, double bonds tend to react to convert the double bond into bonds This is an addition reaction. (Other types of reaction have been substitution and elimination). Addition reactions are typically exothermic. Electrophilic Addition The bond is localized above and below the C-C bond. The electrons are relatively far away from the nuclei and are therefore loosely bound. An electrophile will attract those electrons, and can pull them away to form a new bond. This leaves one carbon with only 3 bonds and a +ve charge (carbocation). The double bond acts as a nucleophile (attacks the electrophile). Ch08 Reacns of Alkenes (landscape) Page 1 In most cases, the cation produced will react with another nucleophile to produce the final overall electrophilic addition product. Electrophilic addition is probably the most common reaction of alkenes. Consider the electrophilic addition of H-Br to but-2-ene: The alkene abstracts a proton from the HBr, and a carbocation and bromide ion are generated. The bromide ion quickly attacks the cationic center and yields the final product. In the final product, H-Br has been added across the double bond. Ch08 Reacns of Alkenes (landscape) Page 2 Orientation of Addition Consider the addition of H-Br to 2-methylbut-2-ene: There are two possible products arising from the two different ways of adding H-Br across the double bond. But only one is observed. The observed product is the one resulting from the more stable carbocation intermediate. Tertiary carbocations are more stable than secondary.
    [Show full text]
  • KEE in Roofing Membranes Only Go So Far – Meaning It Is More Cost-Effective to Use Levels Lower Than Those Required by ASTM D 6754-10
    What is KEE? KEE is an abbreviation for Ketone Ethylene Ester, a high-molecular-weight polymer with elastomeric properties and favorable melting properties for thermoplastic processing. Although KEE is most commonly used in roofing, it is also used in geomembranes for secondary containment for petrochemical storage and other industrial chemical applications. It is manufactured solely by DuPont™, under the brand name Elavloy®. There is also an ASTM International standard, ASTM D 6754-10, which regulates the standards for roofing membranes that use KEE. This standard is commonly referred to as the “KEE Standard” and requires that a minimum of 50% by weight of the polymer content of the roofing membrane be KEE. Therefore all roofing membranes that contain KEE may not comply with the “KEE Standard” but still provide many of the same benefits. Why is KEE used in roofing? This molecule can replace plasticizers in roofing membranes as a solution for flexibility that will not migrate out of the membrane. When mixed with PVC, KEE provides many desirable characteristics in roofing membranes, including: Easy heat welding due to melting properties Resistance to chemical attack Weather resistance Long-term flexibility Durability Resistance to microbial growth Energy efficiency What is the difference between ASTM D 4434-12 and ASTM D 6754-10? ASTM D 4434-12* ASTM D 6754-10 This standard was the first of its kind for A newer standard developed to regulate single ply roofing membranes and the polymer content in roofing membranes. provides a nationally-recognized definition This standard requires a minimum content for PVC membranes. It sets benchmarks of 50% KEE, and also has more strict for PVC content, thickness and other requirements for minimum thickness, physical properties applicable to roofing.
    [Show full text]
  • Aldehydes, Ketones and Carboxylic Acids
    1212Unit Objectives AldehydesAldehydesAldehydesAldehydes,,,,,, KKKKKKeeeeeetonestonestonestonestonestones After studying this Unit, you will be able to andandandandandand CarboxylicCarboxylicCarboxylicCarboxylicCarboxylicCarboxylic • write the common and IUPAC names of aldehydes, ketones and carboxylic acids; AAAAAAcidscidscidscidscidscids • write the structures of the compounds containing functional groups namely carbonyl and carboxyl groups; Carbonyl compounds are of utmost importance to organic chemistry. They are constituents of fabrics, flavourings, plastics • describe the important methods and drugs. of preparation and reactions of these classes of compounds; In the previous Unit, you have studied organic • correlate physical properties and compounds with functional groups containing carbon- chemical reactions of aldehydes, oxygen single bond. In this Unit, we will study about the ketones and carboxylic acids, organic compounds containing carbon-oxygen double with their structures; bond (>C=O) called carbonyl group, which is one of the • explain the mechanism of a few most important functional groups in organic chemistry. selected reactions of aldehydes and ketones; In aldehydes, the carbonyl group is bonded to a carbon and hydrogen while in the ketones, it is bonded • understand various factors to two carbon atoms. The carbonyl compounds in which affecting the acidity of carboxylic carbon of carbonyl group is bonded to carbon or acids and their reactions; hydrogen and oxygen of hydroxyl moiety (-OH) are • describe the uses of aldehydes, known as carboxylic acids, while in compounds where ketones and carboxylic acids. carbon is attached to carbon or hydrogen and nitrogen of -NH2 moiety or to halogens are called amides and acyl halides respectively. Esters and anhydrides are derivatives of carboxylic acids. The general formulas of these classes of compounds are given below: 2021–22 Aldehydes, ketones and carboxylic acids are widespread in plants and animal kingdom.
    [Show full text]