The coordination reaction of 2,3-benzo-6-methyl-15-crown-5, 2,3-benzo-8,12-dimethyl-15-crown-5, 2,3-benzo-15-crown-5 and 15-crown-5 with sodium ion was studied by NMR in acetone to probe the effect of Me at crown ring on coordination ability and some regularities. On adding NaI to the crown solution the chem. shifts of 23Na shifted toward low field for 15C5 similar to that of benzo-derivs. of 18C6 but it shifted toward high field for 15C5 with benzo-ring. The difference may be due to orientation of benzo-ring in crowns. Fitting the data by Newton-Raphson and pit-mapping methods the unstable species Na3L23+ was found to form (L=BC1-15C5 and BC2-15C5) besides NaL+ and NaL2+. The formation reaction of Na3L23+ is discussed. A relationship was found between formation constants lg K11 of NaL and n, the no. of methyls, lg K11 = 3.50-0.48n (n = 0, 1, 2).

Key words: SODIUM COMPOUNDS, THERMODYNAMIC PROPERTIES, CALCULATION, NMR SPECTROMETRY, CROWN ETHER COMPOUNDS, ACETONE, EQUILIBRIUM CONSTANT, CHEMICAL SHIFT, COMPLEX REACTION