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A student loaded a compound mixture onto a column using 2 mL of dichloromethane

ID: 820067 • Letter: A

Question

    A student loaded a compound mixture onto a column using 2 mL of dichloromethane as the loading solvent.  The student then eluted the column using pet roleum ether.  After collecting  8  fractions,  the  student  analyzed  them  by  TLC  to  find  that  all  of  the compounds came off in the first two fractions, with no separation.  Where did the student go wrong?     A student loaded a compound mixture onto a column using 2 mL of dichloromethane as the loading solvent.  The student then eluted the column using pet roleum ether.  After collecting  8  fractions,  the  student  analyzed  them  by  TLC  to  find  that  all  of  the compounds came off in the first two fractions, with no separation.  Where did the student go wrong?     A student loaded a compound mixture onto a column using 2 mL of dichloromethane as the loading solvent.  The student then eluted the column using pet roleum ether.  After collecting  8  fractions,  the  student  analyzed  them  by  TLC  to  find  that  all  of  the compounds came off in the first two fractions, with no separation.  Where did the student go wrong?

Explanation / Answer

He made mistake in running column. He should changed the polarity of the solvent, He should used low polar solvent like pentane, tolune mixture (~ 5 % tolune in hexane).