Open AccessStructures of the monofluoro‐ and monochlorophenols at low temperature and high pressure
Author(s) -
Oswald Iain D. H.,
Allan David R.,
Motherwell W. D. Samuel,
Parsons Simon
Publication year - 2005
Publication title -
acta crystallographica section b
Language(s) - English
Resource type - Journals
eISSN - 1600-5740
pISSN - 0108-7681
DOI - 10.1107/s0108768104030617
Subject(s) - intermolecular force , hydrogen bond , benzene , molecule , crystallization , crystallography , alcohol , chemistry , ambient pressure , materials science , organic chemistry , thermodynamics , physics
2‐Fluorophenol, 3‐fluorophenol and 3‐chlorophenol were recrystallized from frozen solids at 260, 263 and 283 K. All compounds were also crystallized by the application of high pressure (0.36, 0.12 and 0.10 GPa). While 3‐fluorophenol and 3‐chlorophenol yielded the same phases under both conditions, different polymorphs were obtained for 2‐fluorophenol. 4‐Chlorophenol was crystallized both from the melt and from benzene to yield two different ambient‐pressure polymorphs; crystallization from the melt at 0.02 GPa yielded the same phase as from benzene at ambient pressure. 3‐Fluorophenol is unusual in forming a hydrogen‐bonded chain along a 2 1 screw axis. Such behaviour is usually only observed for small alcohols, but here it appears to be stabilized by intermolecular C—H⋯F hydrogen‐bond formation. 3‐Chlorophenol is a more typical large alcohol and emulates a fourfold screw axis with two independent molecules positioned about a 2 1 axis, although there are significant distortions from this ideal geometry. The two phases of 4‐chlorophenol consist of chains or rings connected by C—Cl⋯H interactions. The low‐temperature and high‐pressure polymorphs of 2‐fluorophenol consist of chains of molecules connected through OH⋯OH hydrogen bonds; while inter‐chain C—H⋯F interactions are significant at high pressure, there are none in the low‐temperature form.