Carboxylic acids, esters and triglycerides L.O:  Explain the water solubility of carboxylic acids  Describe the reactions of carboxylic acids with metals, carbonates and bases  Describe the esterification of carboxylic acids with alcohols in the presence of an acid catalyst, and also of acid anhydrides with alcohols  Describe the hydrolysis of esters  Describe a triglyceride as a triester of glycerol and fatty acids.

Homework: carbonyl tests exam questions

-COOH or –CO 2 H CARBOXYLIC ACIDS

Select the longest chain of C atoms containing the COOH group; Remove the e and add oic acid after the basic name Side chain positions are based on the C in COOH being 1. NAMING CARBOXYLIC ACIDS

Name this carboxylic acids: Methanoic acid Ethanoic acid Butanoic acid 2-Bromobutanoic acid 3-methylbutanoic acid

In pairs discuss the solubility of acids. Clues: like dissolves in like, think about intermolecular forces between solvent and solute.

Carboxylate ion Carboxylic acids are weak acids. The equilibrium is well over to the left.

In pairs: deduce the products of the reaction of carboxylic acids with: a)NaOH b)Carbonates c)Na

Esters Made through the esterification reaction from a carboxylic acid and an alcohol

Write out your own esterification reaction between methanol and methanoic acid using structural formula Now draw out the reaction between: 1.Ethanol and ethanoic acid 2.Propanoic acid and hexan-3-ol 3.3,3-dichloro-2-methylhexanoic acid and butan-1-ol 4.Extension work: Name them

Naming esters

Draw these esters and name the alcohols and the carboxylic acids that made them: The smell of oranges is from the ester: 1. Octyl ethanoate Banana is made from: 2. Pentyl ethanoate

Name these esters 1.Found in banana, pineapple, strawberry 2.Found in apple 3.Found in butter and cream 4.

Making esters with acid anhydrides

Hydrolysis of esters When an acid catalyst is used an equilibrium mixture of reactants and products is obtained

Base hydrolysis The salt of an acid is produced. This removes the acid from the reaction mixture so an equilibrium is not established. The reaction goes to completion.

Uses of esters

Oil of wintergreen contains the ester methyl salicylate which is used to help relieve pains in mucles Benzyl ethanoate is used to flavour foods to taste like apples and pears

Fats and oils

Essential to maintain health Solid fats = melting point above room temp, e.g. butter Liquid oils = m.p below room temp, e.g. olive oil Esters of long-chain carboxylic acids.

Name these two fatty acids What does “saturated” and “unsaturated” mean?

Quick questions 1.Draw a molecule of glycerol 2.What is the systematic name for glycerol? 3.How does glycerol combine with fatty acids? 4.What is the name for the bond?

Abbreviating fatty acids