Explain the relative rf values for fluorene , fluorenol, and fluorenone
The Correct Answer and Explanation is :
In chromatography, the relative retention factor (Rf) is a measure of how far a compound travels on a chromatographic medium (like silica gel or alumina) relative to the solvent front. The Rf value is calculated by dividing the distance the compound travels by the distance the solvent front travels.
For the three compounds—fluorene, fluorenol, and fluorenone—here’s an overview of their relative Rf values:
- Fluorene: Fluorene is a non-polar hydrocarbon, meaning it will interact less with the polar stationary phase in chromatography. As a result, fluorene tends to move faster up the plate and thus has a relatively higher Rf value compared to more polar compounds. It has an Rf value that is typically higher than fluorenol and fluorenone.
- Fluorenol: Fluorenol is a hydroxylated derivative of fluorene. The hydroxyl group (-OH) is polar, which means fluorenol will interact more strongly with the polar stationary phase than fluorene. This results in fluorenol moving slower on the chromatographic plate and, consequently, it has a lower Rf value than fluorene.
- Fluorenone: Fluorenone is a ketone derivative of fluorene, containing a polar carbonyl group (C=O). The carbonyl group is even more polar than the hydroxyl group in fluorenol, so fluorenone will interact more strongly with the stationary phase. As a result, fluorenone will move the slowest on the plate and therefore has the lowest Rf value of the three compounds.
Explanation of Relative Rf Values:
The Rf values are influenced by the polarity of the compounds relative to the stationary phase and the mobile phase. In this case, since the stationary phase is typically polar (like silica gel), the more polar compounds (fluorenol and fluorenone) will interact more with the stationary phase, causing them to travel more slowly and giving them lower Rf values. Fluorene, being non-polar, interacts less with the stationary phase and moves more freely, resulting in a higher Rf value.
Thus, the order of Rf values is:
Fluorene > Fluorenol > Fluorenone.