Question

Pre Lab Questions 1. Complete the following table: Compound Acetanilide (A) Benzophenone (B) Mandelic acid (C) Benzil (D) Benzoic acid (E) Structure Solubility in hexanes Solubility in ethyl acetate 2. Using the following diagram of a TLC plate, answer the following questions: solvent front a) Which compound is more polar if the stationary phase is silica gel? b) True or False: If the solvent mixture was made less polar, the compounds would move farther. c) Use a ruler and calculate the Ry value for compounds A and B (show work).

Answer 1

For table of Question 1 find the attached image file.

compound Acadamélide (a) (Benzoplanove hanggang ad Acetanilide Compow a than Benzoi 120 phe one beneity HO Structure COOH OH soluble soluble as less soluble soluble Polar solubility in Insoluble or hexane very less Isolubilityin soluble in fethyl acetate room temp less less soluble more soluble less soluble

2. a) The component B is more polar if silica gel is the stationary phase.

Explanation:

Silica gel is polar structure due to presence of high amount of -OH group in its surface. When silica gel interact with polar component present in solvent system it reacts and bind strongly as a result the polar particle moves very slowly in the plate. On the other hand non polar component moves faster due less interaction so A is non polar than B.

b) False

Explanation:

If the solvent system made less polar then the polar component interact more with the polar stationary phase so it will move further in slow fashion. If we made the solvent system more polar then polar component interacts strongly with the solvent and elution will be fast in this case.

c) Rf value calculation

We now the formula of Rf is Distance travelled by solute/distance travelled by solvent.

It is unitless and maximum value is 1.

So Rf of A = (1.8 cm/ 2.6 cm) = 0.69

Rf of B = (0.8cm/ 2.6 cm) = 0.307