Acta Crystallographica Section B

Structural Science

Volume 63, Part 6 (December 2007)

research papers

Acta Cryst. (2007). B63, 896-902 [ doi:10.1107/S0108768107037263 ]

Compressed hydrogen-bond effects in the pressure-frozen chloroacetic acid

R. Gajda and A. Katrusiak

Abstract: The competing effects of squeezed OHO bonds, destabilizing the H-atom position, and of displaced hydrogen donor and acceptor groups, favouring the ordered H-atom sites, have been tuned by pressure in the pressure-frozen dichloroacetic acid. Its structure has been determined at 0.1, 0.7, 0.9 and 1.4 GPa: in this pressure range the crystals are stable in the monoclinic space group P2₁/n. The molecules are O-HO hydrogen bonded into dimers, which in turn interact via a unique pattern of halogenhalogen contacts. Between 0.1 and 1.4 GPa the OHO bond is squeezed from 2.674 (13) to 2.632 (9) Å. Within the pressure range investigated the hydrogen bonds are squeezed and the shear displacement of the molecules compensate, and the H atoms remain ordered.

Keywords: high pressure; hydrogen bonding; pressure freezing; halogen interactions.


	Structure factor file (CIF format) (25.5 kbytes) [ doi:10.1107/S0108768107037263/av5090dichloroacetic_acid_1sup2.hkl ] Contains datablock dichloroacetic_acid_1

	Structure factor file (CIF format) (23.5 kbytes) [ doi:10.1107/S0108768107037263/av5090dichloroacetic_acid_2sup3.hkl ] Contains datablock dichloroacetic_acid_2

	Structure factor file (CIF format) (9.0 kbytes) [ doi:10.1107/S0108768107037263/av5090dichloroacetic_acid_3sup4.hkl ] Contains datablock dichloroacetic_acid_3

	Structure factor file (CIF format) (7.5 kbytes) [ doi:10.1107/S0108768107037263/av5090dichloroacetic_acid_4sup5.hkl ] Contains datablock dichloroacetic_acid_4

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