Question

column chromatography lab question: what will happen if hexane and dichloromethane are mixed (dichloromethane is run first). how will this be fixed

Answer 1

Solutions:-

When Hexane and dichloromethaneare mixed neither of the two compounds elute off the column, then we can conclude that the solvent is not polar enough to strip the compounds from their affinity to the stationary phase. To fix this, a more polar solvent should be selected for use, but it cannot be too polar otherwise both of the compounds will elute off at the same time.

If the two compounds that you desire to separate elute from the column at the same time, you can conclude that the two halogenated alkenes have too similar of retardation factors for a solvent such as dichloromethane to separate. In order to fix this problem, the student should use two different solvents, starting with a less polar solvent such as petroleum ether and then switch to a more polar solvent such as MtBE. The petroleum ether would elute out the less polar of the two halogenated alkenes while the MtBE would elute out the more polar of the two halogenated alkenes. The use of two different solvents would result in a separation of the two mixed compounds.