Determination of the absolute configuration of (–)-N-ethyl-N-methylaniline oxide by X-ray analysis: the molecular geometry of an N-oxide salt

Abstract

The crystal structure of the (+)-3-bromocamphorsulphonate salt of (–)-N-ethyl-N-methylaniline oxide has been determined in order to establish the absolute configuration of the N-oxide. The crystals of the salt are monoclinic with a= 14·620(4), b= 7·062(5), c= 11·534(5)Å, β= 114° 42′(1′), Z= 2, space group P2₁. The structure was refined to a crystallographic R-factor of 0·050 on 1669 non-zero reflections measured on a diffractometer. The absolute configuration of the N-oxide was established as S by internal comparison to the known absolute configuration of the anion, thus confirming an assignment made previously on the basis of n.m.r. spectral non-equivalence. The important structural parameters in the salt are compared with those in other known structures.