Question

Assume that you synthesized 3-phenylpropioniltrile in the solvent dimethylformamide. A big problem with this solvent is that it has a high boiling point, and it cannot be easily removed under vacuum. Look at a solvent miscibility table, and propose a biphasic mixture that might be useful to extract your organic product without also extracting residual DMF.

Answer 1

Answer:

According to the following solvent miscibility table, the DMF is inmiscible in apolar solvents like hexane, pentane, heptane and xylene. Then, the biphasic mixture will be made with one of those solvents.

Solvent Miscibility Table acetic acid acetone acetonitrile benzene n-butanol butyl acetate carbon tetrachloride chloroform cyclohexane 1,2-dichloroethane dichloromethane dimethylformamide dimethyl sulfoxide dioxane ethanol ethyl acetate diethyl ether heptane hexane methanol methyl-t-butyl ether 2-butanone pentane n-propanol isopropanol diisopropyl ether tetrahydrofuran toluene trichloroethylene water xylene acetic acid acetonitrile carbon tetrachloride n-butanol butyl acetate 1,2-dichloroethane chloroform dichloromethane cyclohexane dimethylformamide dimethyl sulfoxide acetone benzene methyl-t-butyl ether ethyl acetate diethyl ether dioxane ethanol diisopropyl ether methanol trichloroethylene heptane 2-butanone hexane n-propanol tetrahydrofuran pentane isopropanol toluene water xylene = immiscible = miscible

Now, considering the boiling points of these four posibles solvents: hexane (68 ºC), heptane(98.42 ºC), pentane (36.1 ºC) and xylene (144 ºC). the best choice to the binary mixture is the hexane because as extraction solvent it has a ideal boiling point and it is a low-cost solvent. In addittion, the others solvents can be discarded because:

• Heptane and xylene has very high boiling points and they cannot be easily removed under vacuum
• Pentane has a very low boiling point, then a room temperature it could be evaporate easily and the extraction of 3-phenylpropioniltrile won't be satisfactory.

Conclusion: the best sovent o extract the 3-phenylpropioniltrile from DMF is the hexane