Chapter 5, Problem 1Q

Interpretation Introduction

(a)

Interpretation:

Appropriate solvent for the separation of $2$ -phenylethanol and acetophenone is to be determined.

Concept introduction:

Thin layer chromatography or TLC is an analytical technique in which one can separate non-volatile components in a mixture based on polarity of chemical species. There, a sheet of glass, paper, etc. coated with the stationary phase is used which acts as the surface of adsorbent. The components in the sample (dissolved in a mobile phase) move through the stationary phase. Depending on the polarity of stationary phase, some components move faster than other.

Answer to Problem 1Q

Methylene chloride.

Explanation of Solution

  $2$ -phenylethanol is an alcohol. Acetophenone is a ketone. When comparing the two structures one can observe that $2$ -phenylethanol is more polar than acetophenone. Therefore, one need a moderately polar solvent to effectively separate these two components in a mixture. Among the given solvent choices, methyl chloride is moderately polar, which is suitable for the separation of $2$ -phenylethanol and acetophenone. Less polar compounds can travel a great distance from solvent front with less polar solvents.

Interpretation Introduction

(b)

Interpretation:

Appropriate solvent for the separation of bromobenzene and $p$ -xylene is to be determined.

Concept introduction:

Thin layer chromatography or TLC is an analytical technique in which one can separate non-volatile components in a mixture based on polarity of chemical species. There, a sheet of glass, paper, etc. coated with the stationary phase is used which acts as the surface of adsorbent. The components in the sample (dissolved in a mobile phase) move through the stationary phase. Depending on the polarity of stationary phase, some components move faster than other.

Answer to Problem 1Q

Hexane.

Explanation of Solution

Both compounds bromobenzene and $p$ -xylene have a very weak polarity. One can consider them as less polar or nonpolar compounds. Therefore, a nonpolar solvent is needed to separate the components in this mixture because nonpolar compounds can travel a great distance from this solvent front. Hexane is a nonpolar solvent which is suitable for the separation of bromobenzene and $p$ -xylene.

Interpretation Introduction

(c)

Interpretation:

Appropriate solvent for the separation of benzoic acid, $2,4$ -dinitrobenzoic acid and $2,4,6$ -trinitrobenzoic acid is to be determined.

Concept introduction:

Thin layer chromatography or TLC is an analytical technique in which one can separate non-volatile components in a mixture based on polarity of chemical species. There, a sheet of glass, paper, etc. coated with the stationary phase is used which acts as the surface of adsorbent. The components in the sample (dissolved in a mobile phase) move through the stationary phase. Depending on the polarity of stationary phase, some components move faster than other.

Answer to Problem 1Q

Acetone.

Explanation of Solution

All three given compounds benzoic acid, $2,4$ -dinitrobenzoic acid and $2,4,6$ -trinitrobenzoic acid are carboxylic acids. They are highly polar compounds. Therefore, acetone would be the best choice of solvent because it is a highly polar solvent. Polar compounds can travel a great distance from solvent front with polar solvent.