title: Role of chloroform and dichloromethane solvent molecules in crystal packing: an interaction propensity study.
abstract: Using the Cambridge Structural Database (CSD), it is shown that the acidic C-H donors of chloroform and dichloromethane, respectively, form hydrogen bonds with N, O, S, halides or carbon-bound halogens in 82% and 77% of structures in which such interactions can occur. This hydrogen-bond potency is retained to a significant degree even in the presence of the more conventional O-H and N-H donors. The hydrogen-bond propensities exhibited by the C-H protons in CHCl3 and CH2Cl2 are similar to those of the acetylenic C-C≡C-H proton. However, involvement of the Cl atoms of CHCl3 and CH2Cl2 in non-bonded interactions is rather limited: the propensities for formation of (O or N)-H...Cl bonds are only 6% in both cases, while the propensities for the formation of halogen-halogen bonds is generally < 15%, with only Cl...Br interactions having slightly higher values. While C(phenyl)-H...Cl interactions are commonly observed, they are of low propensity and have distances at the upper end of the van der Waals limit. We conclude that the acidic C-H protons in chloroform and dichloromethane solvent molecules play a clear role in the involvement of these molecules in molecular aggregation in crystal structures, and this is exemplified by hydrogen-bond predictions made using the statistical propensity tool which is now part of the CSD system.
authors.affiliation: Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, England. allen@ccdc.cam.ac.uk
authors.forename: Frank H
authors.initials: FH
authors.lastname: Allen
authors.forename: Peter A
authors.initials: PA
authors.lastname: Wood
authors.forename: Peter T A
authors.initials: PT
authors.lastname: Galek
mesh_terms: D002725:Chloroform / Q000737:chemistry*; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D008752:Methylene Chloride / Q000737:chemistry*; D008958:Models, Molecular; D012997:Solvents / Q000737:chemistry
chemical_list: D012997:Solvents; D008752:Methylene Chloride; D002725:Chloroform
keywords: crystal aggregation; crystal packing; hydrogen bonding; interaction propensity study