CRYSTAL-STRUCTURE OF ACETANILIDE AT 15 AND 295 K BY NEUTRON-DIFFRACTION - LACK OF EVIDENCE FOR PROTON-TRANSFER ALONG THE N-H-CENTER-DOT-CENTER-DOT-CENTER-DOT-O HYDROGEN-BOND
Sw. Johnson et al., CRYSTAL-STRUCTURE OF ACETANILIDE AT 15 AND 295 K BY NEUTRON-DIFFRACTION - LACK OF EVIDENCE FOR PROTON-TRANSFER ALONG THE N-H-CENTER-DOT-CENTER-DOT-CENTER-DOT-O HYDROGEN-BOND, Journal of physical chemistry, 99(44), 1995, pp. 16253-16260
The crystal structure of acetanilide C8H9NO, M(r) = 135.17, orthorhomb
ic, space group Pbca, Z = 8, has been determined from neutron diffract
ion data at 15 and 295 K. The following are the crystal data: at 15 K
[295 K], a = 19.467(3) [19.615(3)] Angstrom, b = 9.332(1) [9.474(1)] A
ngstrom, c = 7.735(1) [7.979(1)] Angstrom; V = 1405.2(6) [1482.8(6)] A
ngstrom(3); D-n = 1.2779(1) [1.2110(5)] g . cm(-3), mu(n), = 2.14 [2.0
2] cm(-1), F(000) = 277.46 fm, lambda = 1.0462 Angstrom, R(F-2) = 0.04
7 [0.083], wR(F-2) = 0.060 [0.076], and S = 1.033 [1.000] for 2772 [15
96] reflections (sin theta/lambda < 0.79 [0.68] Angstrom(-1)) and 173
variable parameters. This new investigation of the structure of acetan
ilide has been undertaken in order to assess a recent suggestion that
conformational substates in the amide proton position may be responsib
le for the vibrational anomalies. We found no evidence for multiple co
nformations or transfer along the N-H ... O hydrogen bond of the amide
proton at either temperature. However, the intramolecular O ... H6 di
stance from O to the nearest phenyl ring proton is unusually short and
the amide proton has relatively close contacts with one of the phenyl
and one of the methyl protons, which may well affect the vibrational
parameters of the respective molecular groups.