Organic synthesis
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What further reaction could you do to obtain “soluble” aspirin after recrystallizing the product, and why?
Igloo writes
One problem with aspirin is that it is not particularly soluble in cold, or even warm water (e.g. 36°C – the temperature of the human body). Aspirin’s fairly high solubility in hot water, but relative insolubility in cold water, is the main reason why it can be successfully recrystallized from this liquid.
A medicine tablet works far better if it is water-soluble, because it then enters the blood stream more rapidly. One way of making the aspirin “soluble” is to convert it into one of its salts, e.g. the sodium salt. Since this product is ionic you would expect it to be much more water-soluble than the parent covalent acid - aspirin itself - even if there are some hydrogen bonding opportunities between aspirin and water molecules.
The conversion of aspirin to its sodium salt can be accomplished by neutralizing a portion of your recrystallized sample with aqueous sodium hydroxide or sodium carbonate, and crystallizing out the product using the method normally used for soluble salts.
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Risk assessment
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updated: 15 December 2006
