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TBR Ochem II page 279 #50
“Which combination has the fastest elution time through a column filled with alumina”
C. o-Xylene solute in ligroin
D. Glycine solute in ethanol
Explanation: “Glycine is polar and hydrophilic so despite the presence of ethanol as the eluting solvent, it is still hindered by the alumina” (emphasis added)
“A nonpolar compound like o-xylene exhibits little affinity for the alumina, so it travels quickly down the column. Using a nonpolar solvent like ligroin speeds it up even more”
The first sentence implies that a polar solvent (i.e., ethanol) would decrease elution time.
The second sentence contradicts this.
So do polar solvents or nonpolar solvents travel up polar alumina faster?
“Which combination has the fastest elution time through a column filled with alumina”
C. o-Xylene solute in ligroin
D. Glycine solute in ethanol
Explanation: “Glycine is polar and hydrophilic so despite the presence of ethanol as the eluting solvent, it is still hindered by the alumina” (emphasis added)
“A nonpolar compound like o-xylene exhibits little affinity for the alumina, so it travels quickly down the column. Using a nonpolar solvent like ligroin speeds it up even more”
The first sentence implies that a polar solvent (i.e., ethanol) would decrease elution time.
The second sentence contradicts this.
So do polar solvents or nonpolar solvents travel up polar alumina faster?
