Acetone and isopropyl alcohol are generally not suitable for use in extraction,
ID: 535218 • Letter: A
Question
Acetone and isopropyl alcohol are generally not suitable for use in extraction, but are frequently used as recrystallization solvents. Explain. After separating layers in an extraction, it is necessary to "dry" the organic layer with a substance that absorbs water. Explain why this is necessary. Suggest two methods for determining which layer in an extraction is the aqueous layer and which layer is the organic layer. An organic compound has a distribution coefficient of 1.5 in methylene chloride and water. If 50 mg of this compound is dissolved in 15 ml. of water, in which case will more of the compound he extracted into the methylene chloride: one extraction with 15 mL of methylene chloride or three extractions using 5 mL of methylene chloride each time? Refer to Appendix B if necessary.Explanation / Answer
2 Acetone and isopropyl alcohol are generally not used in extraction as both are miscible in water. The main idea of extraction is to isolate or seperate the compounds in the mixture based on their solubility, extent of formation of hydrogen bonding, polarity or any other factor which works effeciently when the solvents are immiscible and the compounds get distributed effectively. But acetone and isopropyl alcohol are used as recrystallization solvents as they dissolve the compounds not the impurities and at the same time they can effect the polarity of the solution when mixed with polar or nonpolar solvents.
3 Drying the organic layer is nothing but removing any traces of water in the compound that would influence either the purity or the recrystallization process of the compound.
4 Two layers in the extraction process can be easily visible but can be identified
by their densities
take a drop from any layer and ignite, if it burns with a sooty flame it is organic layer,
to little of the layer add salt and observe solubility, if it is soluble it is aqueous layer.