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Alkanoic Acids and Esters

Alkanoic Acids and Esters. SUBSECTION 5 e sterification is a naturally occurring process which can be performed in the laboratory. Methanoic acid (formic acid). Ethanioic acid (acetic acid). Acetyl salicylic acid (aspirin). -COOH. Functional group. The carboxyl acid group.

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Alkanoic Acids and Esters

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  1. Alkanoic Acids and Esters

  2. SUBSECTION 5esterification is a naturally occurring process which can be performed in the laboratory

  3. Methanoic acid (formic acid)

  4. Ethanioic acid (acetic acid)

  5. Acetyl salicylic acid (aspirin)

  6. -COOH Functional group The carboxyl acid group

  7. IUPAC Systematic Naming • count no. carbons in straight chain • select prefix for parent alkane(carbon 1 from –COOH) • drop “e” and add ending –oic acid • formic acid and acetic acid are IUPAC preferred names for methanoic and ethanoic acids

  8. C Ester functional group R = H or alkyl group R1 = alkyl group

  9. Naming Esters ethyl ethanoate • 1st part of name comes from the alkanol • e.g. methanol produces methyl-, ethanol produces ethyl- etc... • 2nd part of name comes from alkanoic acid • e.g. methanoic acid produces –methanoate, ethanoic acid produces –ethanoate etc... ethyl ethanoate

  10. Name this ester

  11. Practice • Name the esters produced from... • Butanol and pentanoic acid • Heptanoic acid and ethanol • Name the alkanols and alkanoic acids used to produce... • Pentyl butanoate • Methyl octanoate

  12. 5.2.3 • explain the difference in melting and boiling point caused by straight-chained alkanoic acids and straight-chained primary alkanol structures

  13. Reactions • alkanoic acids react with alkanols to produce esters (alkyl alkanoates).

  14. Producing Esters • a condensation reaction where two molecules combine with the elimination of a small molecule like water. Alkanol + Alkanoic acid D Ester+ Water

  15. + CH3CH2CH2OH + HOOCCH2CH3 CH3CH2CH2OOCCH2CH3 Example + • The –OH is removed from the ACID • The –H is removed from the ALCOHOL • The C with H atoms attached is from the alcohol • The C without H atoms attached is from the acid

  16. Problem • Use structural formulae to illustrate the reaction of: • Methanol with butanoic acid; • Propanoic acid with ethanol.

  17. Properties of Esters • have pleasant fruity smells • colourless liquids (lower molecular weight are more volatile) • polar molecules • short chain soluble in water • solubility i with h in length of carbon chain • good organic solvents • neutral to Litmus

  18. Esters - Uses • flavours & fragrances • contribute to the tastes and smells of fresh fruits and flowers • used as fragrances in body care products and cosmetics • methyl salicylate used in “Deep Heat” as an emollient to soothe sore muscles

  19. Esters - Uses • lubricants • used as jet engine lubricants for many decades due to their low viscosity • polar molecules – stronger intermolecular forces so lower rates of evaporation and higher flash points

  20. Esters - Uses • solvents • used in wood lacquers and thinners • esters of acetic acid used in personal care products and cosmetics • ethyl acetate in nail polish remover

  21. Esters - Uses • plasticisers • phthalate esters are oily liquids used to soften hard plastics like PVC • plasticised PVC used to make medical tubing, gloves, shower curtains, toys

  22. ASPIRIN (acetyl salicylic acid) an ester of acetic acid and salicylic acid

  23. Triglycerides Triesters of glycerol and fatty acids

  24. Ester+ Water The reverse reaction • The formation of esters is a reversible reaction. • This means that an alkanol and alkanoic acid can be produced from an ester. Alkanol + Alkanoic acid This breakdown using water is called a “hydrolysis” reaction.

  25. Hydrolysis of Esters Ethanoic acid Ethanol CH3COOCH2CH2CH3 CH3COOH CH3CH2CH2OH Ethanoic acid Propan –1- ol

  26. Esterification • slow reaction at room temperature that reaches equilibrium • heating increases the reaction rate, but • the reactants and products with lower boiling points will vaporise readily and be lost ethanol bp 78oC ethanoic acid 114 ethyl ethanoate 77 water 100

  27. Esterification • slow reaction at room temperature that reaches equilibrium • heating increases the reaction rate, but • the reactants and products with lower boiling points will vaporise readily and be lost • heat under reflux – use a cooling condenser vertically over reaction vessel so vapours condense and run back down into reaction flask

  28. Esterification • add conc. H2SO4 as • catalyst to improve reaction rate • dehydrating agent as it removes water so not available for reverse reaction - drives the equilibrium to the right • excess of alkanol shifts equilibrium to the right

  29. Separation of Ester - Fractional Distillation ComponentBoiling point (oC) methanol 64.7 propanoic acid 140.8 water 100 methyl propanoate 79.9

  30. Separation of Ester - Aqueous Separation Draining off the aqueous layer Mixture placed into separating funnel

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