title: Structure of isolated 1,4-butanediol: combination of MP2 calculations, NBO analysis, and matrix-isolation infrared spectroscopy.
abstract: Theoretical calculations at the MP2 level, NBO and AIM analysis, and matrix-isolation infrared spectroscopy have been used to investigate the structure of the isolated molecule of 1,4-butanediol (1,4-BDO). Sixty-five structures were found to be minima on the potential energy surface, and the three most stable forms are characterized by a folded backbone conformation leading to the formation of an intramolecular H-bond. To better characterize the intramolecular interactions and particularly the hydrogen bonds, natural bond orbital analysis (NBO) was performed for the four most stable conformers, and was further complemented with an atoms-in-molecules (AIM) topological analysis. Infrared spectra of 1,4-BDO isolated in low-temperature argon and xenon matrixes show a good agreement with a population-weighted mean theoretical spectrum, and the spectral features of the conformers expected to be trapped in the matrixes were observed experimentally. Annealing the xenon matrix from 20 to 60 K resulted in significant spectral changes, which were interpreted based on the barriers to intramolecular rotation. An estimation of the intramolecular hydrogen bond energy was carried out following three different methodologies.
authors.affiliation: Faculty of Pharmacy, University of Coimbra, 3004-295, Coimbra, Portugal. ajorge@qui.uc.pt
authors.forename: A J Lopes
authors.initials: AJ
authors.lastname: Jesus
authors.forename: Mário T S
authors.initials: MT
authors.lastname: Rosado
authors.forename: Igor
authors.initials: I
authors.lastname: Reva
authors.forename: Rui
authors.initials: R
authors.lastname: Fausto
authors.forename: M Ermelinda S
authors.initials: ME
authors.lastname: Eusébio
authors.forename: J S
authors.initials: JS
authors.lastname: Redinha
mesh_terms: D001128:Argon / Q000737:chemistry; D002072:Butylene Glycols / Q000737:chemistry*; D006860:Hydrogen Bonding; D008958:Models, Molecular; D008968:Molecular Conformation; D011789:Quantum Theory; D013055:Spectrophotometry, Infrared; D013057:Spectrum Analysis; D013696:Temperature; D014732:Vibration; D014978:Xenon / Q000737:chemistry
chemical_list: D002072:Butylene Glycols; D014978:Xenon; D001128:Argon; C039681:1,4-butanediol