Paper chromatography and chemical structure

The chromatographic behaviour of seventy-seven phenols and closely related substances has been studied in a reversed phase system (ethyl oleate against 25 % aqueous ethanol) and the relationships between their R_M values and their structures elucidated and discussed. Constitutive effects in chromatography were studied by means of a new method, the use of atomic ΔR_M parameters. The methods of calculating these parameters for carbon, hydrogen and oxygen are described and illustrated. By this method it is possible to calculate the R_M value of any of these compounds from the R_M value of phenol itself. It is shown that the ΔR_M parameters for CH groups (arbitrarily expressed for convenience as atomic ΔR_M(H) parameters) vary depending on their proximity to the aromatic ring. Similarly, the atomic ΔR_M(O) parameters in ethers are profoundly influenced by the nature of the substituent vicinal to the oxygen atom. These effects are considered to be produced by permanent polarizations due to the resonance effects of alkyl groups in the molecules under consideration.