Question

Predict and explain which of these four compounds (aspirin, acetaminophen, ibuprofen, and caffeine) has the highest Rf value and which one has the lowest Rf value. Refer to their number and polarity of their functional groups to explain the answer in sentence format.

Answer 1

By standard textbook experimentations, we calculate the Rf value of Aspirin, acetaminophen, ibuprofen, and caffeine

and below are the values (refer any standard textbook for these)

aspirin = 0.45

acetaminophen = 0.24

ibuprofen = 0.60

caffeine = 0.08

now based on values, Ibuprofen has highest Rf (Retardation factor) value and Caffiene has lowest Rf value.

when we look at the structure of above-mentioned compounds, we compare their functional group with respect to polarity and number of the functional groups to determine the solvent phase for the chromatography.

Retardation factor - it is defined by the ratio of distance traveled by the solute on a chromatography place by the distance traveled by the solvent phase.

let's say if the solute is very much dissolved in solvent phase then it will travel as much as the solvent itself, in that case, the ratio would be close to one and if the solute is highly insoluble and move very slowly then it will travel very less distance and ration will be close to zero...

Now, this solubility depends on the polarity of functional groups as these groups make the whole compound polar or nonpolar and soluble or insoluble.

Ibuprofen has the highest polarity due to the presence of carboxylic acid and

caffeine has the lowest polarity due to no acidic functional group present. it has C=O groups in the benzene ring.

Answer.