Organic synthesis
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I am investigating how different solvents used for recrystallisation affect the purity of aspirin. Could you please suggest some suitable solvents to for recrystallisation and why they can be used?
Corrie writes
Aspirin is a fairly large organic molecule with polar groups that could hydrogen bond with a solvent, so a polar solvent capable of hydrogen bonding is a good place to start. The presence of the aromatic ring makes this type of molecule less soluble in such solvents.
Hot water is the usual the solvent to purify aspirin in the school laboratory. The aspirin crystallises out easily on colling. One disadvantage of water is that it will slowly hydrolyse the aspirin, especially when hot. Other hydrogen bonding solvents that could be used are alcohols, such as methanol or ethanol. Esters, like ethyl ethanoate, are also good solvents for many polar organic compounds and could be used here.
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updated: 07 January 2008
