why does fluorene elute first from the column
Is it the lightest gas present?
If you have carried out the fluorene to fluorenone oxidation then the fluorene elutes first because it is less polar than the fluorenone.
Fluorene is a polycyclic aromatic hydrocarbon (PAH) that is commonly used as a reference compound in column chromatography. The elution order of compounds in column chromatography is determined by their affinity for the stationary phase and their overall polarity.
In normal-phase column chromatography, which is commonly used for separating nonpolar and moderately polar compounds, the stationary phase is polar (e.g., silica gel) and the mobile phase is nonpolar (e.g., hexane). Compounds that are more polar have a stronger interaction with the stationary phase and therefore elute later, while less polar compounds elute earlier.
Fluorene is less polar compared to many other PAHs. It has a compact structure with fused aromatic rings, which reduces its overall polarity. As a result, it has weaker interactions with the polar stationary phase and tends to elute earlier from the column compared to other more polar PAHs. This behavior is consistent with the principle of "like dissolves like" in chemistry, which states that compounds with similar polarities tend to dissolve or interact with each other.
To determine the elution order of compounds in column chromatography, experimental methods such as thin-layer chromatography (TLC) or the use of reference compounds are typically employed. By comparing the elution behavior of the compound of interest to known standards, the elution order can be determined.