Model for the partition of neutral compounds between n‐heptane and formamide

Partition coefficients for 84 varied compounds were determined for n ‐heptane–formamide biphasic partition system and used to derive a model for the distribution of neutral compounds between the n ‐heptane‐rich and formamide‐rich layers. The partition coefficients, log K p , were correlated through the solvation parameter model giving log K p =0.083+0.559 E –2.244 S –3.250 A –1.614 B +2.387 V with a multiple correlation coefficient of 0.996, standard error of the estimate 0.139, and Fisher statistic 1791. In the model, the solute descriptors are excess molar refraction, E , dipolarity/polarizability, S , overall hydrogen‐bond acidity, A , overall hydrogen‐bond basicity, B , and McGowan's characteristic volume, V . The model is expected to be able to estimate further values of the partition coefficient to about 0.13 log units for the same descriptor space covered by the calibration compounds ( E =−0.26–2.29, S =0–1.93, A =0–1.25, B =0.02–1.58, and V =0.78–2.50). The n ‐heptane–formamide partition system is shown to have different selectivity to other totally organic biphasic systems and to be suitable for estimating descriptor values for compounds of low water solubility and/or stability.