Alcohols Noadswood Science, 2013

Alcohols To understand the structure of alcohols Wednesday, April 25, 2018 Alcohols To understand the structure of alcohols

Alcohols Alcohols have an –OH functional group, with the general formula CnH2n+1OH Methanol – CH3OH Ethanol – C2H5OH Propanol – C3H7OH

Alcohol Uses Alcohols are flammable, burn to produce CO2 and H2O, are used as solvents / fuels Ethanol is used for alcoholic drinks

Alcohol As Solvents Alcohols such as methanol and ethanol can dissolve most compounds that water dissolves but they can also dissolve substances that water cannot, such as oils, fats and hydrocarbons Ethanol is the solvent for perfumes and aftershaves (it can mix with the oils (giving the smell) and the water) Methylated spirits (meths) is ethanol with other chemicals such as ethanol added to it – meths are used as pain cleaners and fuels (though they are poisonous to drink so are dyed)

Alcohol As Fuels Ethanol is used as a fuel as it burns cleanly, and it can also be mixed with petrol (which reduces pollution) Brazil have little oil, but lots of land to grow sugar cane for ethanol / petrol mix

Ethanol Ethanol is the type of alcohol found in alcoholic drinks such as wine and beer Ethanol is also useful as a fuel – for use in cars and other vehicles, it is usually mixed with petrol

Ethene + Steam  Ethanol Ethanol can be manufactured by reacting ethene (from cracking crude oil) with steam –phosphoric acid is used as a catalyst: - Ethene + Steam  Ethanol C2H4+ H2O C2H5OH In the reaction ethanol is the only product – the process is continuous as long as ethene and steam are fed into one end of the reaction vessel, ethanol will be produced These features make it an efficient process, but as ethene is made from crude oil, which is a non-renewable resource, it cannot be replaced once it is used up and it will run out one day

Ethanol & Fermentation Ethanol can also be made via fermentation – sugar from plant material is converted into ethanol and carbon dioxide… Enzymes found in single-celled fungi (yeast) are the natural catalysts that can make this process happen (this is a renewable resource): - C6H12O6  2C2H5OH + 2CO2 More than 90% of the world’s ethanol is made by fermentation