In a chemical process step, the unseparated mixture of positional isomers of xylene is cheap enough to serve as either a reaction solvent or solvent for use in purification.
I am always on the lookout for pairs of organic solvents that can serve as immiscible phases for solute partitioning by liquid-liquid extraction since this is a very robust, simple, and scalable purification method.
Although toluene is immiscible with wet DMSO, it is miscible when thoroughly dried. However, the commercial xylene mixture is reported to be immiscible with even dry DMSO. This mixture of positional isomers also is reported to give two liquid phases with dimethylformamide and trichloroethylene. The extra saturated carbon apparently makes the difference.
Of the three combinations:
xylenes/DMSO
xylenes/DMF
xylenes/ trichloroethylene
the final one seems the most remarkable. I would appreciate it if someone who is actually in a lab (I am retired) would either confirm or disavow it in the comment section. It would be very interesting to see how different compounds are partitioned between these two.
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