Question

The idea is to design an experiment to synthesize Compound B from Compound A. I have the idea in mind. I wrote out the stochiometry, the reaction mechanism and most of the procedure... I need help with separation and purification of the compounds. I'm using column chromatography for this. I have a mixture of Compound B (C₁₀H₉O₂Cl) - Solubility in 10mL hexane of 0.4 and solubility in 10 mL ethyl ether of 0.8 and also Compound C (C₁₀H₁₁O₃Cl) which is the byproduct - solubility in the 10mL hexane of 0.44 and in the 10mL of ethyl ether of 0.5. How do I go about doing the separation and purification???? I know the tube is packed with cotton and silica or alumina. What solvent do I use and how do I prepare this? Thank you!

Answer 1

By merely knowing the solubility sepration of both compound B and C is not possible or even if someone gives just a judgment, I am not sure how much it will be accurate. Insted, looking at the solubility well experianced organic chemist can suggest you to do the TLC analysis. Start devloping TLCs from less polar solvent misxture such as only in hexane. Both compounds do have some solubility in hexane means both will run on TLC and give some sepration. If sepration is not observed then go for increasing the polarity of solvent to devlop TLC. You can prepare TLC solvent by making 2% Ethyl acetate (EtOAC) + 98% hexane, if this solvent does not make any seperation in spot of B and C the go for further increasing the polarity by making solvent of 5% EtOAC + 95% Hexane. You can gradually increase the polarity of TLC solvent and confirm the mixture of solvent (let's say 10% EtOAc + 90% hexane) gives better separation, then load the column with your mixture of B+C. The give first run of only hexane, second run of 5% EtOAC + 95% Hexane and then run column with constant mixture of 10% EtOAc + 90% hexane.

This will help in getting better seperation. While collecting fractions always check for the mixture. Discard or re-do the column sepration for fractions containing mixture.

If EtOAc and hexane does not work then you may increase polarity by adding portion wise methanol aswell.