title: Understanding the Reactivity and Regioselectivity of Methylation of Nitronates [R(1)R(2)CNO2](-) by CH3I in the Gas Phase.
abstract: Methylation of [R(1)R(2)CNO2](-), where R(1) = R(2) = H (1), R(1) = CH3 and R(2) = H (2), R(1) = R(2) = CH3 (3), and R(1) + R(2) = c-(CH2)2 (4), by CH3I was studied by an ab initio MP2/CBS method, RRKM theory, and kinetic simulations. Contrary to a previous proposal for the reaction mechanism, C-methylation is the preferred pathway of thermodynamics and kinetics. This is corroborated by the agreement between the calculated and experimental reactivity trend 4 ≫ 3 > 2 > 1. The regioselectivity toward C-alkylation is explained by the much larger exothermicity of this reaction channel compared to that of O-alkylation. The increase in reactivity with an increase in the crowdedness of the central carbon atom is explained by differences in sp(3) character at this atom and the decrease in the vibrational frequency associated with pyramidalization around this carbon atom.
authors.affiliation: Departamento de Química Fundamental, Universidade Federal de Pernambuco, Cidade Universitária, Recife, PE 50740-560, Brazil.
authors.forename: Ayyaz
authors.initials: A
authors.lastname: Mahmood
authors.affiliation: Departamento de Química Fundamental, Universidade Federal de Pernambuco, Cidade Universitária, Recife, PE 50740-560, Brazil.
authors.forename: Erico Souza
authors.initials: ES
authors.lastname: Teixeira
authors.affiliation: Departamento de Química Fundamental, Universidade Federal de Pernambuco, Cidade Universitária, Recife, PE 50740-560, Brazil.
authors.forename: Ricardo L
authors.initials: RL
authors.lastname: Longo