Question

Relatively polar compound X will have the highest Rf value when eluted on a silica gel TLC plate in which of the following solvents?

		hexanes
		hexanes/ethyl acetate 3:1
		hexanes/ethyl acetate 1:1
		hexanes/ethyl acetate 1:2

Answer 1

Rf value is defined as the ratio of distance travelled by the sample to the distance travelled by the solvent front.

Since the compound is polar, it will move more distance in polar compositions, which results in higher Rf values.

Thus as the percentage of ethyl acetate (polar solvent) , the Rf value increases

Thus maximum Rf value will be For 1:3 hexane: ethyl acetate mixture

The increasing order is

Hexane, 1:1, 1:2,1:3 hexane: ethyl acetate mixture

Maximum Rf value will be For 1:3 hexane: ethyl acetate mixture