Absolute configuration of chiral ethanol-1-d: Neutron diffraction analysis of the (-)-(1S)-camphanate ester of (+)-(R)-ethanol-1-d

The absolute configuration of (+)-ethanol-1-d has been determined to be R by the single-crystal neutron diffraction analysis of its (-)-camphanate ester. The absolute configuration of the (-)camphanate group, which sewed as the chiral reference for the neutron study, was in turn established to be 1S,4R in an X-ray anomalous dispersion study of the complex Cu-2(camphanate)(4)-(ethanol)(2), These results provide unambiguous confirmation that the optical rotation of(R)-ethanol-1-d (positive) is opposite to that of its higher homologs, (R)-propanol-1-d, (R)-butanol-1-d, and (R)-neopentanol-1-d (all negative), and demonstrates the usefulness of neutron diffraction in determining the absolute configuration of molecules possessing chiral methylene groups (i.e., molecules of the type CHDRR'). Crystallographic details: for the neutron analysis of(+)-(R)-ethyl-1-d (-)-(1S)-camphanate: space group P2(1)2(1)2 (orthorhombic), a=6.422(1) Angstrom, b=21.004(4) Angstrom; c=9.275(2) Angstrom, V = 1251.1(7) Angstrom(3), Z = 4; R(F-2) = 0.083, and wR(F-2) = 0.075 for 1114 reflections. For the X-ray analysis of Cu-2(camphanate)(4)(ethanol)(2): space group P1 (triclinic), a = 11.086(3), b = 11.244(3), c = 13.293(4) Angstrom, alpha = 111.59(2), beta = 107.71(2), and gamma = 105.56(3)degrees, V = 1397.6(7) Angstrom(3), Z = 1; R(F)=0.054, wR(F) = 0.058 for 3672 reflections.