title: The conformational analysis of 2-halocyclooctanones.
abstract: The establishment of the most stable structures of eight membered rings is a challenging task to the field of conformational analysis. In this work, a series of 2-halocyclooctanones were synthesized (including fluorine, chlorine, bromine and iodine derivatives) and submitted to conformational studies using a combination of theoretical calculation and infrared spectroscopy. For each compound, four conformations were identified as the most important ones. These conformations are derived from the chair-boat conformation of cyclooctanone. The pseudo-equatorial (with respect to the halogen) conformer is preferred in vacuum and in low polarity solvents for chlorine, bromine and iodine derivatives. For 2-fluorocyclooctanone, the preferred conformation in vacuum is pseudo-axial. In acetonitrile, the pseudo-axial conformer becomes the most stable for the chlorine derivative. According to NBO calculations, the conformational preference is not dictated by electron delocalization, but by classical electrostatic repulsions.
authors.affiliation: Departamento de Química, Universidade Estadual de Maringá, Av. Colombo, 5790, 87020-900 Maringá, PR, Brazil.
authors.forename: Thiago C
authors.initials: TC
authors.lastname: Rozada
authors.affiliation: Departamento de Química, Universidade Estadual de Maringá, Av. Colombo, 5790, 87020-900 Maringá, PR, Brazil.
authors.forename: Gisele F
authors.initials: GF
authors.lastname: Gauze
authors.affiliation: Departamento de Química, Universidade Estadual de Maringá, Av. Colombo, 5790, 87020-900 Maringá, PR, Brazil.
authors.forename: Fernanda A
authors.initials: FA
authors.lastname: Rosa
authors.affiliation: Instituto de Quimica, Universidade Estadual de Campinas, 13083-970 Campinas, SP, Brazil.
authors.forename: Denize C
authors.initials: DC
authors.lastname: Favaro
authors.affiliation: Instituto de Quimica, Universidade Estadual de Campinas, 13083-970 Campinas, SP, Brazil.
authors.forename: Roberto
authors.initials: R
authors.lastname: Rittner
authors.affiliation: Departamento de Química, Universidade Estadual de Maringá, Av. Colombo, 5790, 87020-900 Maringá, PR, Brazil.
authors.forename: Rodrigo M
authors.initials: RM
authors.lastname: Pontes
authors.affiliation: Departamento de Química, Universidade Estadual de Maringá, Av. Colombo, 5790, 87020-900 Maringá, PR, Brazil. Electronic address: eabasso@uem.br.
authors.forename: Ernani A
authors.initials: EA
authors.lastname: Basso
mesh_terms: D034242:Cyclooctanes / Q000737:chemistry*; D004583:Electrons; D006219:Halogens / Q000737:chemistry*; D007659:Ketones / Q000737:chemistry*; D008968:Molecular Conformation; D013055:Spectrophotometry, Infrared; D013816:Thermodynamics
chemical_list: D034242:Cyclooctanes; D006219:Halogens; D007659:Ketones; C044494:cyclooctanone
keywords: Conformations; Halocyclooctanones; Infrared; Theoretical calculations