jo970615n_si_001.pdf (467.6 kB)
Absolute Configuration of Chiral Ethanol-1-d: Neutron Diffraction Analysis of the (−)-(1S)-Camphanate Ester of (+)-(R)-Ethanol-1-d
journal contribution
posted on 1997-07-25, 00:00 authored by Tobias Metzenthin, André Schreiber, Richard K. McMullan, Thomas F. Koetzle, Harry S. Mosher, Robert BauThe 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 served 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
Cu2(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 P21212
(orthorhombic), a = 6.422(1) Å, b =
21.004(4) Å, c = 9.275(2) Å,
V = 1251.1(7) Å3, Z = 4;
R(F2) = 0.083, and
wR(F2) = 0.075 for 1114
reflections. For the X-ray
analysis of
Cu2(camphanate)4(ethanol)2:
space group P1 (triclinic), a = 11.086(3),
b = 11.244(3), c
= 13.293(4) Å, α = 111.59(2), β = 107.71(2),
and γ = 105.56(3)°, V = 1397.6(7)
Å3, Z = 1; R(F)
=
0.054, wR(F) = 0.058 for 3672
reflections.