Basics
Periodic Table
Industrial

Organic Chem.
Alcohols
Alkanes and Alkenes
Esters
Homologous Series
Polymers

Analytic

Alcohols

The alcohols are another homologous series of compounds that have the general formula CnH2n+1OH.

The Series

The names of the alcohols follow the same pattern as the alkanes and the alkenes. Here are the first few, their name, chemical and structural formula:

MethanolEthanolPropanolButanol
CH3OHC2H5OHC3H7OH C4H9OH

Manufacturing Ethanol

There are two methods of manufacturing ethanol, either from ethene or sugar.

Producing it from ethene is more common in developed countries like those in North America and Europe where ethene is widely available. The following reaction between ethene and steam takes place with a phosphoric acid catalyst at 600°C and high pressure.

reaction between ethene and steam to produce ethanol

The production of ethanol using sugar is more common in developing nations with less oil and ethene but alot of agricultural produce. This method also can make use of material that would have otherwise gone to waste.

Plant material is fermented for several days, and the following reaction takes place:

Gluscose Ethanol + Carbon Dioxide
C6H12O6 (aq) 2C2H5OH (aq) + 2CO2 (g)

The ethanol produced is combustible so can be used in car engines. This has become known as biofuel, and it was originally thought to provide a more environmentally friendly source of fuel to replace fossil fuels. However it appears to do more harm than good by reducing the supply of food and encouraging deforestation to plant crops that can be fermented.

Uses

Ethanol is by far the most commonly used alcohol, and has numerous applications, including:

  • As a solvent for paints and perfumes. When the product is applied, the ethanol evaporates.

    • It is used as fuel. Most notably in Brazil, where either pure ethanol or a mix with petrol is used to fuel the majority of cars. This can be a carbon neutral way to fuel transport (see above) because, although carbon dioxide is produced in combustion, manufacturing it by fermentation means all CO2 is absorbed by growing the plants to ferment.

  • For making other compounds like ethanoic acid (see below) or esters.

  • Ethanol is the "alcohol" that is in alcoholic drinks.

    • Ethanoic Acid

    Formerly known as acetic acid, it is a type of carboxylic acid with the molecular formula of C2H4O2 and structural formula of:

    structural formula of ethanoic acid

    It is the acid in vinegar, and so if a wine is left, the ethanol in it oxidises to become ethanoic acid:

    Ethanol + Oxygen ® Ethanoic Acid + Water
    C2H5OH + O2 ® CH3COOH + H2O