Question

Which compound will have the larger rf value on a si02 tlc plate using 10 % ethyl acetate/ hexane as eluent: 3-decanone or 3-decanol, toluene or benzoic acid, cyclooctane or cyclooctanone? why?

Answer 1

The formula of determining the $R_f$ value is:

$R_f = \frac{distance travelled by the solute}{distance travelled by the solvent}$

where both the distance are measured from the common origin.

10 % ethyl acetate/ hexane means it has 10 % ethyl acetate and 90 % hexane which are non-polar in nature. Hence, the non-polar compound will travel farther in the TLC plate along with the eluent and the polar compound will travel less as they remain attracted to the polar adsorbent $SiO_2$.

Among 3-decanone and 3-decanol, 3-decanone will have high $R_f$ as it is non-polar.

Among toluene and benzoic acid, toluene will have high $R_f$ as it is non-polar.

Among cyclooctane and cyclooctanone, cyclooctane will have high $R_f$ as it is non-polar.