Why does fluorene move faster down the column chromatography than fluorenone?

Answer 1

Well it depends on the solvent you are using, but lets assume you use pentane as the solvent for fluorene and diethyl ether as the solvent for fluorenone. Used in this order, fluorene should actaully move slower down the column due to the the polarity of the alumina and the nonpolarity of the solvent (pentane). Since fluorene is less polar so, remember the rule like dissolves like? Well, this kind of applies to chromatography wherein rather than dissolve just replace it with moves with, so like moves with like. That being said the pentane will "carry" the fluorene through the alumina slower than the latter (which I will explain). Fluorenone is polar because of its C=O bond, that being said the dielectric constant of diethyl ether is 4.3 which means it has intermediate polarity (remember that pentane has a dielectric constant of 2.1 I think, so it is nonpolar). Since the alumina, diethyl ether, and the fluorenone are all polar, the fluorenone will travel faster through the alumina than would the fluorene, because there is no attraction between all these polar compounds which will allow it to move faster, rather than a nonpolar and polar chemical having an attration towards each other and thus moving more slowly.

Hope this helps,

Branden

Answer 2

fluorenone is more polar compound than fluorene, at the same time silica gel is polar compound, then polar compound will that is fluorenone will be retained or absorbed in the stationary phase whereas fluorene will be eluted out

Answer 3

be cause of its polarity