CI 13.5 - Esters
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- Created on: 03-10-15 11:03
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- CI 13.5 - Esters
- Formation of Esters
- Alcohol and carboxylic acid heated together under reflux in the presence of a few drops of concentrated sulphuric acid.
- Water is formed as a by product, known as a condensation reaction.
- Condensation reaction - two molecules reacting together to form a larger molecule with the elimination of a small molecule.
- Ester link formed by the condensation reaction of hydroxyl group and the carboxyl group. known as esterification.
- Esterification reaction is reversible, therefore controlled according to Le Chatelier's Principle.
- Yield can be increased by: distilling off water as product or increasing concentration of cheap alcohol. Both move the position of equilibrium to the right.
- Reversible reaction is ester hydrolysis.
- Esterification reaction is reversible, therefore controlled according to Le Chatelier's Principle.
- Uses of Esters
- Commonly used in food flavourings and perfumes
- This is due to their strong sweet smells, often floral or fruity.
- Ethyl butanoate - strawberry
- 3-methylbutyl ethanoate - banana
- 2-prop-1-enyl hexanoate - pineapple
- Commonly used in food flavourings and perfumes
- Naming Esters
- Named after alcohol and carboxylic acid from which they are derived.
- Esters end in -oate
- The first part comes from the alcohol. If it were ethanol, the preffix would be ethyl
- The suffix is derived from the acid. If it were butanoic acid, the name would end in butanoate.
- Group attached to C=O from the acid. Group attached to -O- from the alcohol.
- Esters end in -oate
- Named after alcohol and carboxylic acid from which they are derived.
- Polyesters
- Condensation polymers. Made by reacting a diol with a dicarboxylic acid.
- Common polyester made from ethane-1,2-diol and benzene-1,4-dicarboxylic acid.
- Also A-B polymerisation. Diol being A polymer and dicarboxylic acid being B.
- Common polyester made from ethane-1,2-diol and benzene-1,4-dicarboxylic acid.
- Condensation polymers. Made by reacting a diol with a dicarboxylic acid.
- Making Esters from Phenols
- -OH group in phenol less reactive to esterification than -OH group of ethanol. Needs more vigorous reagent.
- When ethanoic acid involved in esterification, process known as ethanoylation.
- More vigorous ethanoylating agent is ethanoic anhydride. Made by eliminating molecule of water between two ethanoic acid molecules.
- Ethanoic anhydride and ethanoyl chloride members of general group of reagents called acylating agents.
- When ethanoic acid involved in esterification, process known as ethanoylation.
- Phenol treated with acid anhydride under reflux.
- Phenol reacts with acyl chloride under room temperature.
- Both reactions must be carried out in absence of water
- Both reactions must be carried out in absence of water
- Phenol reacts with acyl chloride under room temperature.
- -OH group in phenol less reactive to esterification than -OH group of ethanol. Needs more vigorous reagent.
- Formation of Esters
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