Question

The student loads the solid onto a column, prepacked with silica gel, and elutes the column with an appropriate solvent system to allow the components to be completed separated. 11. Based on your understanding of column chromatography, which of the following solvent systems is most likely to yield the best separation of the two components in this mixture? Please explain your answer BRIEFLY (5 pts)! The ranking of solvent polarity is: MeOH>ethyl acetate> hexane (ie, MeOH is the most polar). a. MeOH/hexane followed by ethyl acetate/hexane b. Pure ethyl acetate followed by ethyl acetate/hexane C. Ethyl acetate/hexane followed by pure ethyl acetate 12. Which compound, indicating just the letter, elutes (comes off the column) first (5 pts)? Finally, the student has isolated the desired product from this reaction. However, the sample still is not sufficiently pure, and as a result, it is recrystallized. Solubility (g/100 mL) Solvent Hot Cold 2.0 1.5 1.5 0.1 0.5 0.3 13. Based on the solubility data provided above, which solvent is best for this recrystallization (3 pts)? 14. Assuming the student recovered 0.57 g of product from the column chromatography experiment, and 0.47 g after recrystallization, please set up the calculation that would provide the percent recovery (for the recrystallization: 5 pts).

Answer 1

11) In column chromatography , non-polar compounds elute first followed by polar ones. From the above mixture Ethylacetate -hexane mixture is the best system for separation of compounds. As hexane is the most non-polar solvent & ethyl acetate is polar one mixture separate components step by step as per the increase in polarity of the solvents (2%, 5%, 10% etc) & finally pure ethyl acetate.

12) The non-polar compound will elute in initial fractions.

13) Solvent II is best for recrystallisation .

14) % recovery = 0.47/ 0.47+0.57*100 = 33%