Running Head: Column Chromatography
Experiment 9: Column Chromatography (Post-laboratory Questions)
Experiment 9: Column Chromatography
1. Predict the order of elution of a mixture of triphenylmethanol, biphenyl, benzoic acid,
and methyl benzoate from an alumina column.
The alumina column uses the same mechanism as the TLC plate to separate
chemicals. The chemical to elute first is the least polar one as it moves faster while
the chemical to elute last is the most polar one as it moves faster. This is because a
compounds polarity is dependent on the functional groups. We determinje the polar
functional group for every compound and it follows that methyl benzoate has ester (CO2R), carboxylic acid (-CO2H) is contain in Benzoic acid, aromatic hydrocarbons
are contain in Biphenyl and hydroxyl group (-OH) is contain in Triphenylmethanol as
Therefore, the polarity order for these functional groups is as follows:
Aromatic < Ester < Hydroxyl < Carbonxylic acid. This implies that benzoic acid is
the most polar eluting last while biphenyl is the least polar eluting first. The order
thus is: Biphenyl, methyl benzoate, triphenymethanol, and benzoic acid.
2. What would have been the result if a large quantity of petroleum ether alone were used
as the eluent in the experiment you just performed?
It is worth noting that petroleum ether is actually not an in the sense of functional group,
but it is a composition of isomeric pentanes. It is nonpolar since it is comprises of
aliphatic hydrocarbons, a solvent that is less polar compared to hexanes. Moreover, the
first two experiments involves eluting columns using hexanes. This implies that the
elution of the two compounds using petroleum ether, the compounds will even be slower.
Therefore, a lot of ...