Experimental measurement of noncovalent interactions between halogens and aromatic rings.
Chemical double mutant cycles have been used to quantify the interactions of halogens with the faces of aromatic rings in chloroform. The halogens are forced over the face of an aromatic ring by an array of hydrogen-bonding interactions that lock the complexes in a single, well-defined conformation. These interactions can also be engineered into the crystal structures of simpler model compounds, but experiments in solution show that the halogen-aromatic interactions observed in the solid state are all unfavourable, regardless of whether the aromatic rings contain electron-withdrawing or electron-donating substituents. The halogen-aromatic interactions are repulsive by 1-3 kJ mol(-1). The interactions with fluorine are slightly less favourable than with chlorine and bromine.
Adams
Harry
H
Centre for Chemical Biology, Krebs Institute for Biomolecular Science, Department of Chemistry, University of Sheffield, Sheffield, S3 7HF, UK.
Cockroft
Scott L
SL
Guardigli
Claudio
C
Hunter
Christopher A
CA
Lawson
Kevin R
KR
Perkins
Julie
J
Spey
Sharon E
SE
Urch
Christopher J
CJ
Ford
Rhonan
R
D018360:Crystallography, X-Ray; D006219:Halogens / Q000138:chemical synthesis / Q000737:chemistry*; D006841:Hydrocarbons, Aromatic / Q000138:chemical synthesis / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D013237:Stereoisomerism
D006219:Halogens; D006841:Hydrocarbons, Aromatic