Organic molecules

Table of Contents

1. Organic molecules
2. Hydrocarbons
   1. Names and structures of hydrocarbons
3. Reactions of hydrocarbons
   1. Substitution reactions
   2. Addition reactions
4. Functional groups
   1. Identifying functional groups
5. Alcohols
   1. Structure of alcohols
   2. Physical properties of alcohols
6. Reactions of alcohols
   1. Oxidation reactions
   2. Carboxylic acids
   3. Alcohols, carboxylic acids and esters
   4. Identification of alcohols
7. Nitrogen in organic molecules
   1. Amines
   2. Amino acids
8. Determination of formulae and structures
   1. Empirical formulae
   2. Molecular mass and formula

1. Additional resources:
   1. Glossary
   2. Print content

Reactions of alcohols

The presence of the -OH functional group allows alcohols to undergo a series of reactions.

Combustion

They are generally highly flammable and can be used as fuels.

When combusted in a supply of air or oxygen they will burn to form carbon dioxide and water as shown by these two examples.

2 CH₃OH + 3 O₂ → 2 CO₂ + 4 H₂O

(Methanol)

CH₃CH₂OH + 3 O₂ → 2 CO₂ + 3 H₂O

(Ethanol)

Petrol in Australia can contain up to 10% ethanol. Ethanol does not release quite as much energy per litre as the main component of petrol, octane. However, it does burn efficiently (generally with a cleaner flame than alkanes), and produces slightly less carbon dioxide.

Other oxidation reactions

Combustion is a type of oxidation, but more interesting are other oxidation reactions of alcohols.

When our bodies absorb alcohol, oxidation reactions convert the ethanol into other products such as aldehydes which can be removed from the body.

Oxidation reactions are also the cause of foods and drinks containing alcohol 'going off', such as wine converting to vinegar in the presence of oxygen.

It is in these reactions that primary, secondary and tertiary alcohols behave very differently as you will see later.

Reactions with carboxylic acids

These reactions, which are called condensation reactions, produce another type of organic chemical called esters.