Conformational analysis of 2-halocyclopentanones by NMR and IR spectroscopies and theoretical calculations

Author(s)

Martins, Carina R. ^[1] ; Ducati, Lucas C. ^[1] ; Tormena, Claudio F. ^[1] ; Rittner, Roberto ^[1]

Affiliation

^[1] State Univ Campinus, Inst Chem, Phys Organ Chem Lab, BR-13084971 Campinas, SP - Brazil

• Document type: Journal article
• Source: SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY; v. 72, n. 5, p. 1089-1096, JUN 2009.
• Web of Science Citations: 5

Abstract

The conformational isomerism of 2-chlorocyclopentanone and 2-bromocyclopentanone has been determined through the solvent dependence of the (1)H NMR (3)J(HH) coupling constants, theoretical calculations and infrared data, using the solvation theory for the treatment of NMR data. In 2-chlorocyclopentanone, the energy difference (E(psi-r) - E(psi-a)), in the isolated molecule at B3LYP level of theory, between the pseudo-equatorial (psi-e) and pseudo-axial (psi-a) conformers is 0.42 kcal mol(-1), which decreases ill CCl(4) and in acetonitrile Solutions. in good agreement with infrared data (vc=o), despite the uncertainties of the latter method. The conformational equilibrium for 2-bromocyclopentanone is also between the psi-e and psi-a conformations, with an energy difference (E(psi-p) - E(psi-a)), in the isolated molecule at B3LYP level of theory, is 0.85 kcal mol(-1) which decreases in CCl(4) and in acetonitrile Solutions, also in good agreement with infrared data. (C) 2009 Elsevier B,V. All rights reserved. (AU)

• FAPESP's process: 05/59649-0 - Conformational equilibria studies by nuclear magnetic resonance spectroscopy, infrared spectroscopy and theoretical calculations
• Grantee: Roberto Rittner Neto
• Support Opportunities: Research Projects - Thematic Grants