title: Vibrational spectroscopy of 3,4-difluorocyclobutenes: cis-d0, trans-d0 and trans-d4 species.
abstract: Infrared and Raman spectra were recorded for cis-3,4-difluorocyclobutene (cDFCB) and trans-3,4-difluorocyclobutene-d4. Unscaled density functional theory (DFT) calculations of frequencies and intensities at the B3LYP/6-311++G(d,p) level supported the complete assignment of the vibrational fundamentals. The previous assignment of fundamentals of trans-3,4-difluorocyclobutene was revised. An unusual blue shift occurs for the methylenic CH-stretching frequencies of cis-3,4-difluorocyclobutene in going from the gas phase to the liquid phase. This hydrogen bond effect is related to similar observations recently reported and interpreted. The blue shift does not occur for the vinylic CH bonds of the cis isomer and does not occur for either type of CH bond in the trans isomer.
authors.affiliation: Department of Chemistry, Oberlin College, 119 Woodland Street, Oberlin, OH 44074, USA. norm.craig@oberlin.edu
authors.forename: Norman C
authors.initials: NC
authors.lastname: Craig
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Brickey
authors.forename: Peter T
authors.initials: PT
authors.lastname: Lingenfelter
authors.forename: A Sonan
authors.initials: AS
authors.lastname: Osmani
authors.forename: M Osman
authors.initials: MO
authors.lastname: Rathore
authors.forename: Ann
authors.initials: A
authors.lastname: Pearson
mesh_terms: D003503:Cyclobutanes / Q000737:chemistry*; D005466:Fluorocarbons / Q000737:chemistry; D005740:Gases; D006838:Hydrocarbons; D006845:Hydrocarbons, Fluorinated / Q000737:chemistry*; D006860:Hydrogen Bonding; D008697:Methane / Q000031:analogs & derivatives / Q000737:chemistry; D008958:Models, Molecular; D013053:Spectrophotometry / Q000379:methods*; D013055:Spectrophotometry, Infrared; D013059:Spectrum Analysis, Raman / Q000379:methods*; D013696:Temperature
chemical_list: D003503:Cyclobutanes; D005466:Fluorocarbons; D005740:Gases; D006838:Hydrocarbons; D006845:Hydrocarbons, Fluorinated; C030011:carbene; D008697:Methane