These studies together show for some reaction families, hydrogen bonding Figure : Differing solvent parameters versus the epoxidation rate of βcaryophyllene; data from . Rate correlates well with the difference between solvent's hydrogen bond donor and acceptor characters, Σα H 2 -Σβ H 2 , but not with dielectric constant . with solvent is more important than polarity to explain kinetic solvent effect. However, treating the solvent explicitly is occasionally necessary to deduce these effects, as was the case of HFIP vs. methanol .