Extraction of Sodium Picrate by 3m-Crown-m Ethers and Their Monobenzo Derivatives (m = 5, 6) into Benzene: Estimation of Their Equilibrium-Potential Differences at the Less-Polar Diluent/Water Interface by an Extraction Method

Table 3

A measure of basic parameters for a comparison between Ls.

L	Cavity size (parameter: )	Molecular volume ()	Number of donor O atoms ()	Basicity of donor O atoms ()	Softness of ring skeleton ()	Na^+ selectivity ()
15C5	1	0	5	2	2	2
B15C5	1	2	5	1	1	2
18C6	2	1	6	2	2	0
B18C6	2	3	6	1	1	0
DB18C6	2	4	6	0	0	0