1 chem lab questi, easy

2010-10-05 5:51 pm

1.) During the synthesizing an important pharmaceutical , an impure solid was obtained as one of the intermediates, the qualitative solubility of this intermediate in various solvents is shown below.

water: insoluble in cold,slightly soluble in hot
ethanol: soluble in cold and hot
toluene: insoluble in cold, soluble in hot
petroleum ether: insoluble in cold and hot
2-butanone: soluble in cold and hot
acetic acid: slightly soluble in cold, soluble in hot

Which solvent would be best for recrystallization of this intermediate? Explain. Also explain why ethanol and petroleum ether are not suitable recrystallization solvents.

回答 (1)

己式庚辛

2010-10-06 7:15 am

✔ 最佳答案

toluene.
for recrystallization, the solvent must dissolve the compound when hot, and precipitate them as much as possible when cold (to maximize the recovery).

ethanol is not suitable. the compound is soluble no matter in hotness or coldness. it cannot be precipitated and extracted from the solvent by precipitation after cooling.

pet. ether is not suitable. since the compound cannot dissolve anyway, impurities inside cannot be extracted and removed by precipitation of purer compound from the solution.

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