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Type: Artigo de periódico
Title: Conformational behaviour of methyl 2-fluoroesters through theoretical calculations, NMR and IR spectroscopy
Author: Tormena, CF
Freitas, MP
Rittner, R
Abraham, RJ
Abstract: The conformational equilibrium of methyl 2-fluoropropionate (1) was studied through a combination of NMR, theoretical calculations and solvation theory. IR spectroscopy was used as an auxiliary technique for this analysis. The (1)J(CF) couplings were analysed using theoretical and solvation calculations to give conformer energies in the solvents studied, vapour phase energies, and also the coupling constants for the distinct rotamers. The trans rotamer is more stable than the cis rotamer in the vapour phase by 0.4 kcal mol(-1) and the conformers are of equal energy in CCl4. The more polar cis form is the major rotamer in the remaining solvents studied. Theoretical evaluation at the B3LYP/6-311++g(d,p) level for the alpha-alkyl substituent effect was carried out using methyl 2-fluorobutyrate (2), methyl 2-fluoro-tert-butylacetate (3) and methyl 2-fluorophenylacetate (4) as models, and showed the great effect of these substituents on the conformational stabilities. The governing interactions of these systems were rationalised in terms of both classical and non-classical effects, such as steric, electrostatic, O...H-C hydrogen bonding, gauche effect and hyperconjugative interactions.
Country: Inglaterra
Editor: Royal Soc Chemistry
Rights: embargo
Identifier DOI: 10.1039/b311570d
Date Issue: 2004
Appears in Collections:Unicamp - Artigos e Outros Documentos

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