Esters, all properties


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A general view of all chemical and physical properties of esters. Ass well as their daily use and structure ;)

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Esters, all properties

  1. 1. Esters
  2. 2. What are esters? ☺ ☺ ☺
  3. 3. Esters occur naturally, but can be made in the laboratory by reacting an alcohol with an organic acid. A little sulfuric acid is needed as a catalyst. This is the general word equation for the reaction: alcohol + organic acid → ester + water For example: methanol + butanoic acid → methyl butanoate + water The diagram shows how this happens, and where the water comes from:
  4. 4. Names of esters end in –oate. Naming Named after alcohol & carboxylic acid from which they are derived. O C CH3 CH2 ethyl This part comes from the alcohol & is named after it CH3 O ethanoate This part from the acid and is named after it
  5. 5. Esterification Esterification is the reaction of a carboxylic acid and alcohol in the presence of an acid catalyst to produce an ester. The main chain of an ester comes from the carboxylic acid, while the alkyl group in an ester comes from the alcohol.
  6. 6. Ester hydrolysis Breakdown of an ester by water. Process sped up by catalysis Can use an acid to catalyse (H2SO4) Alkali catalysts (e.g. sodium hydroxide) can also be used but instead of producing carboxylic acid a carboxylate salt is formed. Alkaline hydrolysis goes to completion & hence is usually preferred.
  7. 7. Carboxylic acids can be esterified using diazomethane: RCO2H + CH2N2 → RCO2CH3 + N2 Using this diazomethane, mixtures of carboxylic acids can be converted to their methyl esters in near quantitative yields, e.g., for analysis by gas chromatography. The method is useful in specialized organic synthetic operations but is considered too expensive for large scale applications.
  8. 8. Alcoholysis of acyl chlorides and acid anhydrides • Alcohols react with acyl chlorides and acid anhydrides to give esters: RCOCl + R'OH → RCO2R' + HCl (RCO)2O + R'OH → RCO2R' + RCO2H • The reactions are irreversible simplifying work-up( refers to the series of manipulations required to isolate and purify the product of a chemical reaction). Since acyl chlorides and acid anhydrides also react with water, anhydrous conditions are preferred. This method is employed only for laboratory-scale procedures, as it is expensive.
  9. 9. Transesterification • Involves changing one ester into another one.It is widely practiced: RCO2R' + CH3OH → RCO2CH3 + R'OH Like the hydrolysation, transesterification is catalysed by acids and bases. • The reaction is widely used for degrading triglycerides, e.g. in the production of fatty acid esters and alcohols. Poly(ethylene terephthalate) is produced by the transesterification of dimethyl terephthalate and ethylene glycol: (C6H4)(CO2CH3)2 + 2 C2H4(OH)2 → 1/n {(C6H4)(CO2)2(C2H4)}n + 2 CH3OH
  10. 10. Carbonylation Alkenes undergo "hydroesterification" in the presence of metal carbonyl catalysts. Esters of propionic acid are produced commercially by this method: C2H4 + ROH + CO → C2H5CO2R The carbonylation of methanol yields methyl formate, which is the main commercial source of formic acid. The reaction is catalyzed by sodium methoxide: CH3OH + CO → CH3O2CH
  11. 11. Addition of carboxylic acids to alkenes • In the presence of palladium-based catalysts, ethylene, acetic acid, and oxygen react to give vinyl acetate: C2H4 + CH3CO2H + 1/2 O2 → C2H3O2CCH3 + H2O
  12. 12. One of the organic chemical reactions known to ancient man was the preparation of soaps through a reaction called saponification. Natural soaps are sodium or potassium salts of fatty acids, originally made by boiling lard or other animal fat together with lye or potash (potassium hydroxide). Hydrolysis of the fats and oils occurs, yielding glycerol and crude soap.
  13. 13. Bar Soaps Soap is made by combining lye (sodium hydroxide is the chemical name) with a liquid and fats and oils. Once these ingredients are mixed, a chemical reaction starts to take place. The result of this reaction is soap and if you've made it right, there isn't any lye left. Just good clean glycerin rich soap. Liquid Soaps The major difference between bar soaps and liquid soaps is the alkali used to saponify the oils. All soap, whether hard or liquid, starts with a simple chemical reaction between oils and an alkali. With bars soaps, it's sodium hydroxide. With liquid soaps, it's potassium hydroxide.
  14. 14. Odors and smells One of the most important physical property of esters is their variety of smells. They occur naturally in plants and animals. Small esters, in combination with other volatile compounds, produce the pleasant aroma of fruits. In general, a symphony of chemicals is responsible for specific fruity fragrances; however, very often one single compound plays a leading role. For example, an artificial pineapple flavor contains more than twenty ingredients but ethyl butyrate is the major component that accounts for the pineapple-like aroma and flavor. It is amazing that so many fragrances and flavors can be prepared by simply changing the number of carbons and hydrogens.
  15. 15. Name Flavor or Fragrance Propyl acetate Pears Octyl acetate Oranges Isoamyl acetate Banana Ethyl Butyrate Pineapple Butyl acetate Apple Methyl transcinnamate Strawberry
  16. 16. Perfumes Property Why the property is important? non-toxic does not poison the wearer does not irritate the skin prevents the wearer from suffering rashes evaporates easily - very volatile perfume molecules reach the nose easily insoluble in water it is not washed off easily does not react with water avoids the perfume reacting with perspiration
  17. 17. Aspirin and Salicylic Acid Aspirin -is used to relieve pain and reduce inflammation -is an ester of salicylic acid and acetic acid Oil of wintergreen -is used to soothe sore muscles -is an ester of salicylic acid and methanol
  18. 18. Bleona Çoba & Anxhela Blloshmi