title: Reactivity in nucleophilic vinylic substitution (S(N)V):S(N)Vπ versus S(N)Vσ mechanistic dichotomy.
abstract: The intrinsic electronic factors that determine reactivity in prototypical identity nucleophilic vinylic substitution reactions, X(-) + ViX → XVi + X(-) (Vi = vinyl), have been studied by performing quantum chemical calculations (OPBE/6-311++G(d,p)). Of the two limiting reaction types envisaged--the S(N)Vπ and S(N)Vσ mechanisms--the former is preferred for most combinations of nucleophiles and substrates, except for the combination of unactivated substrates and poor nucleophiles, as seen for the much studied reactions Cl(-) + CH2CHCl and Br(-) + CH2CHBr. It was found that periodic trends for S(N)Vπ are essentially the same as those previously reported for nucleophilic aromatic substitution, S(N)Ar, while intrinsic S(N)Vσ nucleophilicity parallels aliphatic S(N)2. It is therefore concluded that S(N)V reactivity in general can be understood in terms of this mechanistic dichotomy. Furthermore, a few representative reactions were analyzed applying two complementary schemes for energy decomposition analysis.
authors.affiliation: Departamento de Química Orgánica, Facultad de Química, Universidad Complutense, 28040-Madrid, Spain.
authors.forename: Israel
authors.initials: I
authors.lastname: Fernández
authors.forename: F Matthias
authors.initials: FM
authors.lastname: Bickelhaupt
authors.forename: Einar
authors.initials: E
authors.lastname: Uggerud
mesh_terms: D015394:Molecular Structure; D011789:Quantum Theory; D014752:Vinyl Chloride / Q000737:chemistry*; D014753:Vinyl Compounds / Q000737:chemistry*
chemical_list: D014753:Vinyl Compounds; C003763:vinyl bromide; D014752:Vinyl Chloride