Comparison of crystal structures of new racemic chiral compounds showing and not showing the phenomenon of preferential enrichment

The crystal structures of (+/-)-[2-[4-(3-ethoxy-2-hydroxypropoxy)phenylcarb amoyl]ethyl] trimethylammonium p-chlorobenzenesulfonate [(+/-)-NCMe3] and i ts terminal methoxy derivative, (+/-)-NeMe3-OMe, are compared. The former r acemate exhibited the phenomenon of Preferential Enrichment, whereas the la tter failed to de so. Crystal data, (+/-)-NCMe3: CuK alpha radiation, space group P (1) over bar, Z = 2, a = 9.848(5), b = 14.823(3), c = 9.147(1) Ang strom, alpha = 97.81(2), beta = 92.68(3), gamma = 105.92(2)degrees, D-calc = 1.355 g/cm(3), R = 0.056 for 3213 observed reflections; (+/-)-NCMe3-OMe: CuK alpha radiation, space group P (1) over bar, Z=2, a = 11.350(1), b=14.5 68(2), c = 8.2981(4) Angstrom, alpha = 94.346(7), beta = 112.356(5), gamma = 78.622(9)degrees, D-calc = 1.343 g/cm(3), R = 0.069 for 1519 observed ref lections.