Conformational analysis of 2,2-difluoroethylamine hydrochloride: double gauche effect

Autor(es)

Silla, Josue M. ^[1] ; Duarte, Claudimar J. ^[2] ; Cormanich, Rodrigo A. ^[2] ; Rittner, Roberto ^[2] ; Freitas, Matheus P. ^[1]

Afiliação do(s) autor(es)

^[1] Univ Fed Lavras, Dept Chem, BR-37200000 Lavras, MG - Brazil

^[2] Univ Estadual Campinas, Inst Chem, Campinas, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Beilstein Journal of Organic Chemistry; v. 10, p. 877-882, APR 16 2014.
• Citações Web of Science: 7

Resumo

The gauche effect in fluorinated alkylammonium salts is well known and attributed either to an intramolecular hydrogen bond or to an electrostatic attraction between the positively charged nitrogen and the vicinal electronegative fluorine atom. This work reports the effect of adding a fluorine atom in 2-fluoroethylamine hydrochloride on the conformational isomerism of the resulting 2,2-difluoroethylamine chloride (2). The analysis was carried out using NMR coupling constants in D2O solution, in order to mimic the equilibrium conditions in a physiological medium, in the gas phase and in implicit water through theoretical calculations. Despite the presence of sigma(CH)->sigma({*})(CF) and sigma(CH)->sigma({*})(CN) interactions, which usually rule the hyperconjugative gauche effect in 1,2-disubstituted ethanes, the most important forces leading to the double gauche effect (+NH3 in the gauche relationship with both fluorine atoms) in 2 are the Lewis-type ones. Particularly, electrostatic interactions are operative even in water solution, where they should be significantly attenuated, whereas hyperconjugation and hydrogen bond have secondary importance. (AU)

• Processo FAPESP: 11/01170-1 - Estudos físico-químicos de compostos orgânicos: interações de longa distância e análise conformacional de compostos organofluorados
• Beneficiário: Rodrigo Antonio Cormanich
• Modalidade de apoio: Bolsas no Brasil - Doutorado
• Processo FAPESP: 12/03933-5 - Equilíbrios conformacionais e interações intramoleculares em uma série de aminoácidos: abordagem teórica e experimental
• Beneficiário: Roberto Rittner Neto
• Modalidade de apoio: Auxílio à Pesquisa - Regular
• Processo FAPESP: 11/11098-6 - Análise conformacional de alguns ésteres metílicos de aminoácidos e seus N-acetil-derivados.
• Beneficiário: Claudimar Junker Duarte
• Modalidade de apoio: Bolsas no Brasil - Doutorado