Esterification and

dehydration of

alcohols

Starter:Use molecular models to make various alcohol molecules

Keywords:Esterification, elimination, ester, dehydration

Learning Objectives

A Model the esterification of alcohols with carboxylic acids

B Describe the elimination of H2O from alcohols to form alkenes.

C Name the esters formed by esterification reactions

Esterification – the reaction of an alcohol with a carboxylic acid to produce an ester and water

Elimination – breaking up 1 molecule into 2 molecules

Dehydration – an elimination reaction in which water is removed from a saturated molecule to make an unsaturated molecule

Esterification

An ester is formed when an alcohol is warmed with a carboxylic acid in the presence of an acid catalyst

The reaction is known as esterification

Concentrated sulfuric acid is often used as the acid catalyst

The esterification reaction between Propanoic acid and Methanol

In the reaction, the O-H bond in the alcohol is broken and water is formed.

The water molecule comes from the OH of the carboxylic acid group and the H in

the alcohol group

Naming esters

Choose an alcohol and a carboxylic acid card. Name the ester and draw its structure.

X-yl X-anoate

Carboxylic acidAlcohol

Esters are used as adhesives and solvents in the chemical industry. The

flavours and fragrances of different esters are widely used to produce food

flavourings and perfumes.

Preparing an ester

1. In a boiling tube add 1cm3 carboxylic acid to 1cm3 alcohol and

add the catalyst (H2SO4)

2. Place tube in a water bath (80C) for 5 mins

3. Pour the product into a beaker of cold

water4. The oil on the surface

will be the ester

Dehydration of an alcohol

An alcohol can be dehydrated to form an alkene in the presence of an acid catalyst (Conc phosphoric acid or conc sulphuric

acid)

This is an elimination reaction

Alcohol is heated under reflux with the catalyst for 40 minutes.

The dehydration of cyclohexanol is seen below. What is the product?

Plenary

Pg 155

Questions 1, 2 and 3

Methanol Methanoic acid

Ethanol Ethanoic acid

Propanol Propanoic acid

Butanol Butanoic acid

Pentanol Pentanoic acid

Hexanol Hexanoic acid