Carboxylic acids, esters and Carboxylic acids, esters and triglyceridestriglycerides

L.O:Explain the water solubility of carboxylic acidsDescribe the reactions of carboxylic acids with metals, carbonates and basesDescribe the esterification of carboxylic acids with alcohols in the presence of an acid catalyst, and also of acid anhydrides with alcoholsDescribe the hydrolysis of estersDescribe a triglyceride as a triester of glycerol and fatty acids.

Homework: carbonyl tests exam questions

O

O H-COOH or –CO2H

CARBOXYLIC CARBOXYLIC ACIDSACIDS

• 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 ACIDSNAMING CARBOXYLIC ACIDS

Name this carboxylic acids:

CO

OHH

C

H

H

CO

OHH

C C

H

C

H H

H

CO

OH

H

H

H

C C

H

C

H Br

H

CO

OH

H

H

H

C C

H

C

CH3

H

H

CO

OH

H

H

H

CH3COOH

CH3CH3CH2COOH

CH3CH2CHBrCOOH

CH3CH(CH3)CH2COOH

HCOOH 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.

R CO

O HR C

O

O+ H+

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)NaOHb)Carbonatesc) Na

CH3COOH(aq) + Na2CO3(aq) CH3COONa(aq) + H2O(l) + CO2(g)2 2

CH3COOH(aq) + NaHCO3(aq) CH3COONa (aq) + H2O (l) + CO2(g)

CH3COOH(aq) + NaOH(aq) CH3COONa(aq) + H2O

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 ethanoateBanana is made from: 2. Pentyl ethanoate

Name these esters1. Found in banana,

pineapple, strawberry

2. Found in apple

3. Found in butter and cream

4.

Making esters with acid anhydrides

Hydrolysis of esters

R C

O

O C2H5

R C

O

O H

CH2H5OH+ H2OH+ catalyst

+

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

Base hydrolysis

R C

O

O C2H5

R C

O

O H

CH2H5OH

NaOH

R C

O

O Na+

+ H2O +

++ H2O

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

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

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 glycerol2. 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