2.7 Alcohols and Carboxylic acids

Reactions including industrial productions and different types of alcohols and carboxylic acids.

General formula of an alcohol

CnH2n+1OH

How are the structures of alcohols classified?

Primary (1º), Secondary (2º), Tertiary (3º)

Primary Alcohol (1º)

The OH is joined to a carbon that has 1 R group and 2 H atoms

Secondary Alcohol (2º)

The OH is joined to a carbon that has 2 R groups and 1 H atom

Tertiary Alcohol (3º)

The OH is joined to a carbon that has 3 R groups and no H atoms.

Hydration of ethene conditions

• steam and ethene

• Conc phosphoric acid

• 300ºC

• Pressure = 60-70 atm.

How is ethanol removed from the mixture of gasses?

Fractional distillation (close boiling points.)

Fermentation conditions

• Yeast

• Sugar

• Anaerobic

• Warm temperature

Boiling point of ethanol

Approximately 80ºC

Bioethanol

Obtained from sugars in plants by fermentation.

Biodiesel

Obtained from oils and fats present in the seeds of some plants.

Advantages of Biofuels

• Renewable

• Carbon neutral

• Economic and political security

Disadvantages of Biofuels

• Land use

• Uses of resources

• Lots of CO2 produced.

Uses of ethanol

• Solvent

• Alcoholic drinks

• Fuel

• Cleaning

Dehydration of alcohols to form alkenes conditions.

• Concentrated sulphuric acid

• 170ºC

• OR heated aluminium oxide at 360ºC

What type of reaction is the dehydration of alcohols?

Elimination reaction

Oxidising agent for oxidation of alcohols.

Potassium dichromate

Test for alcohols (1º and 2º)

• acidified potassium dichromate (VI) → orange to green.

• acidified potassium manganate (VII) → Purple to colourless.

What are primary alcohols oxidised to?

Aldehydes then, oxidise further to carboxylic acid.

Conditions for oxidation of primary alcohols.

• heat (distillation)

• heat under reflux for aldehyde → carboxylic acid.

What are secondary alcohols oxidised to?

Ketones (E.g. H3C-(C=O)-CH3)

Conditions for oxidation of secondary alcohols.

Heat under reflux

What do tertiary alcohols oxidise to?

Tertiary alcohols can’t oxidise.

Carboxylic acids general formula

C_nH_2n+1COOH

Why are carboxylic acids acidic?

They release H+ ions into water.

What is esterification?

Carboxylic acids react with alcohols to form esters.

Conditions for esterification?

• Heat

• Conc sulphuric acid

How to make a pure sample of an ester?

Simple distillation.

General equation for esterification

Carboxylic acid + Alcohol ⇌ Ester + Water