jp047187r_si_007.cif (11.51 kB)
Electron and Nuclear Positions in the Short Hydrogen Bond in Urotropine-N-oxide·Formic Acid
dataset
posted on 2005-03-10, 00:00 authored by Cara L. Nygren, Chick C. Wilson, John F. C. TurnerThe crystal structure of urotropine-N-oxide·formic acid, as determined from multiple temperature single-crystal X-ray diffraction experiments in the range 123−295 K and from neutron diffraction at 123 K, is
reported. There is a strong hydrogen bonding interaction between the OH of formic acid and the N-oxide of
urotropine, with the oxygen−oxygen distance ranging from 2.4300(10) to 2.4469(10) Å. The electron density
of the hydrogen atom associated with this interaction was located in the Fourier difference maps of the spherical
atom refinement after all heavy atom positions were determined. The maximum of the electron density
associated with the hydrogen bond is located approximately 1.16 Å from the formate segment, though the
distribution of electron density is very broad. The electron density associated with the H atom is thus shown
by these accurate X-ray diffraction experiments to be approximately centered at all temperatures studied.
This was conclusively confirmed by single-crystal neutron diffraction data obtained at 123 K, from which
statistically equivalent O−H distances of 1.221(7) and 1.211(7) Å were obtained.