Friday 17 August 2012


What is the relationship between structure and Rf value?


Best Answer - Chosen by Voters

Rf stands for the retention factor in chromatography. It is a measure of how strongly the substituents are attached (adsorp) to the stationary phase. The stronger the adsorption, the lower is the Rf value.

Rf can be calculated by dividing the distance covered by the substituent with distance covered by the mobile phase.

A bulky structure ( branched isomer) has a weaker bond compared to a straight chained isomer. This is because the area of contact betweeen molecules is less compared to the straight chained isomer. ( van der Waal forces) Hence it moves faster and have a higher Rf value.

A molecule that can form hydrogen bond will have a lower Rf value compared to molecule with van der Waals as its intermolecular force of attraction. 

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