The element effect revisited: factors determining leaving group ability in activated nucleophilic aromatic substitution reactions.

ABSTRACT: The "element effect" in nucleophilic aromatic substitution reactions (S(N)Ar) is characterized by the leaving group order, F > NO(2) > Cl ≈ Br > I, in activated aryl halides. Multiple causes for this result have been proposed. Experimental evidence shows that the element effect order in the reaction of piperidine with 2,4-dinitrophenyl halides in methanol is governed by the differences in enthalpies of activation. Computational studies of the reaction of piperidine and dimethylamine with the same aryl halides using the polarizable continuum model (PCM) for solvation indicate that polar, polarizability, solvation, and negative hyperconjugative effects are all of some importance in producing the element effect in methanol. In addition, a reversal of polarity of the C-X bond from reactant to

SUBMITTER: Senger NA 

PROVIDER: S-EPMC3498977 | biostudies-literature | 2012 Nov

REPOSITORIES: biostudies-literature