Question

Which is the MOST polar? Which is the LEAST polar? Explain your reasoning. (and have the lowest and highest Rf values)

1) beta-carotene

2) lysine

3) tryptophan

Answer 1

The correct order of given compounds from least polar to most polar is as follows:

Beta-carotene (least polar) < tryptophan < lysine (most polar)

Beta carotene is the hydrocarbon molecule and does not contains any polar atom. Thus, it is least polar.

Tryptophan is the amino acid containing indole side chain. Since, it contains polar amine and carboxylic acid functional groups it is more polar than beta carotene.

Lysine is also amino acid containing polar amine functional group on side chain. Due to presence of two amine functional groups and one carboxylic acid functional group, lysine is most polar.

Least polar compounds have highest Rf value and most polar compounds have lowest Rf values. Therefore, beta carotene has highest Rf value and lysine has lowest Rf value.