The synthesis, infrared spectra, and crystal structures of three isomeric dicyclohexano-14-crown-4 diols

Abstract

From the hydrogenation of the cis-dihydroxydibenzo-14-crown-4 (I), three isomeric dicyclohexano-14-crown- diols were isolated and separated by fractional crystallisation. X-Ray crystal structure analyses established the relative configuration of: isomer (A), m.p. 134 °C, as (cis-1,6,9,20-trans-12,17)-9,20-dihydroxy-7,11,18,22-tetraoxatricyclo[16.4.0.0^12,17]docosane; isomer (B), m.p. 118 °C, as (cis-1,6,9,12,17,20)-9,20-dihydroxy-7,11,18,22-tetraoxatricyclo[16.4.0.0^12,17]docosane; and isomer (C),m.p. 170 °C, as (cis-1,6,12,17-trans-9,20)-9,20-dihydroxy-7,11,18,22-tetraoxatricyclo[16.4.0.0^12,17]docosane. For isomer (B) measurements were by neutron diffraction. The hydrogen bonding in each crystalline from correlates well with the i.r. spectra. In isomer (B)one hydroxy hydrogen does not take part in hydrogen bounding, the other gives a bond with an O ⋯ O distance of 2.925(2)Å(neutron). In isomers (A) and (C) each hydroxy hydrogen atom may occupy one of two sites yielding disordered hydrogen bonds of the type O–H ⋯ O or O ⋯ H–O; the O ⋯ O distances average 2.822(2)Å in isomer (A) and 2.76(1)Å in isomer (C). The packing is also discussed in relation to the melting points and densities.