title: Microwave and infrared spectra, adjusted r0 structural parameters, conformational stabilities, vibrational assignments, and theoretical calculations of cyclobutylcarboxylic acid chloride.
abstract: The FT-microwave spectrum of cyclobutylcarboxylic acid chloride, c-C4H7C(O)Cl, has been recorded and 153 transitions for the (35)Cl and (37)Cl isotopologues have been assigned for the gauche-equatorial (g-Eq) conformation. The ground state rotational constants were determined for (35)Cl [(37)Cl]: A = 4349.8429(25) [4322.0555(56)] MHz, B = 1414.8032(25) [1384.5058(25)] MHz, and C = 1148.2411(25) [1126.3546(25)] MHz. From these rotational constants and ab initio predicted parameters, adjusted r0 parameters are reported with distances (Å) rCα-C = 1.491(4), rC═O = 1.193(3), rCα-Cβ = 1.553(4), rCα-Cβ' = 1.540(4), rCγ-Cβ = 1.547(4), rCγ-Cβ' = 1.546(4), rC-Cl = 1.801(3) and angles (deg) τCγCβCβ'Cα = 30.9(5). Variable temperature (-70 to -100 °C) infrared spectra (4000 to 400 cm(-1)) were recorded in liquid xenon and the g-Eq conformer was determined the most stable form, with enthalpy differences of 91 ± 9 cm(-1) (1.09 ± 0.11 kJ/mol) for the gauche-axial (g-Ax) form and 173 ± 17 cm(-1) (2.07 ± 0.20 kJ/mol) for the trans-equatorial (t-Eq) conformer. The relative amounts at ambient temperature are 54% g-Eq, 35 ± 1% g-Ax, and 12 ± 1% t-Eq forms. Vibrational assignments have been provided for the three conformers and theoretical calculations were carried out. The results are discussed and compared to corresponding properties of related molecules.
authors.affiliation: Department of Chemistry, University of Missouri-Kansas City, Kansas City, Missouri 64110, United States.
authors.forename: Joshua J
authors.initials: JJ
authors.lastname: Klaassen
authors.forename: Ikhlas D
authors.initials: ID
authors.lastname: Darkhalil
authors.forename: Bhushan S
authors.initials: BS
authors.lastname: Deodhar
authors.forename: Todor K
authors.initials: TK
authors.lastname: Gounev
authors.forename: Ranil M
authors.initials: RM
authors.lastname: Gurusinghe
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Tubergen
authors.forename: Peter
authors.initials: P
authors.lastname: Groner
authors.forename: James R
authors.initials: JR
authors.lastname: Durig