DAT Destroyer 2014 OChem Question #10

[urbanthread]

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Question: What methods are used for the separation of p-Nitroaniline and o-Nitroaniline?

Answer: First, use crystallization to crystallize out para with solvent ethanol (ortho will not crystallize). Then, run mother liquor thru a column (column chromatography) to purify ortho.

Could someone please explain why para crystallizes but ortho doesn't? Also, after you isolate the crystals, why do you have to run a column chromatography to purify ortho when you already separated para and ortho? Thank you!

 

[Potential22]

the question is asking about which methods, so both column chromatography (aka thin layer chromatogrophy) and crystallization are both separation technique while IR isnt. since para is more symmetrical, it is going to crystallize first, i believe ortho since it is not as symmetrical it doesnt pack compactly thus does not crystallize.

 

[biomolecmed]

Whenever a molecule has symmetry it has a higher melting point because it can fit into a crystal very well comparing to the molecule that does not have symmetry.