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Noadswood Science, 2013. Alcohols. Alcohols. To understand the structure of alcohols. Alcohols. Alcohols have an –OH functional group, with the general formula C n H 2n+1 OH Methanol – CH 3 OH Ethanol – C 2 H 5 OH Propanol – C 3 H 7 OH. Alcohol Uses.
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Noadswood Science, 2013 Alcohols
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
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