The crystal and molecular structures of 4,6‐diethoxy‐1‐ethylpyrimidinium tetrafluoroborate and 6‐ethoxy‐1,3‐diethyl‐1,4(3,4)‐dihydro‐4‐oxopyrimidinium tetrafluoroborate, two isomeric reaction products of 4,6‐diethoxypyrimidine with Meerwein reagent

Abstract

AbstractThe crystal and molecular structures of two isomeric compounds, 4,6‐diethoxy‐1‐ethylpyrimidinium tetrafluoroborate and 6‐ethoxy‐1,3‐diethyl‐1,4(3,4)‐dihydro‐4‐oxopyrimidinium tetrafluoroborate, reaction products of 4,6‐diethoxypyrimidine with Meerwein reagent [O(C2H5)+3 BF−4], have been determined by means of X‐ray diffraction.4,6‐Diethoxy‐1‐ethylpyrimidinium tetrafluoroborate is monoclinic a = 10.794, b = 13.361, c = 10.892 Å, β = 112.6°, space group P21/n, four molecules per unit cell.6‐Ethoxy‐1,3‐diethyl‐1,4(3,4)‐dihydro‐4‐oxopyrimidinium tetrafluoroborate is monoclinic, a = 17.637, b = 14.054, c = 11.501 Å, β = 101.7°, space group C2/c, eight molecules per unit cell.In both structures the fluoroborate ions are disordered. The bond distances in the π‐electron systems are reasonably well described in terms of a small number of resonance structures.