Crystal structure of (7R,9R,18S,20S)-6,7,9,10,17,18,20,21-octahydro-7,9,18,20-tetramethyldibenzo[b,k][1,4,7,10,13,16]hexaoxacyclo-octadecin (tetramethyldibenzo-18-crown-6, isomer F)

Abstract

Crystals of the title compound are triclinic, with a= 8·726(6), b= 8·746(8), c= 9·600(7) A, α= 107·92(6), β= 117·47(4), γ= 98·35(5)°, Z= 1, space group P. The crystal structure has been determined by direct methods and refined by least squares to R 0·057 on 980 diffractometer data. The molecule has crystallographic symmetry with torsion angles differing from the trans-C–O and gauche-C–C pattern found in complexed polyethers. Mean bond lengths are: C–C(aliphatic) 1·508(8), C–C(aromatic) 1·382(5), C(sp³)–O 1·431(4), and C (sp)²–O 1·364(6)Å. The differences in conformation from dibenzo-18-crown-6 are caused by steric effects of the methyl groups.