title: Conformational Equilibrium and Internal Dynamics of E-Anethole: A Rotational Study.
abstract: The rotational spectra of the two conformers of E-anethole have been investigated using the free jet broadband millimeter-wave spectroscopic technique combined with theoretical calculations. Anti and syn conformers differ for the relative orientation of the propenyl and methoxy chains, with all heavy atoms coplanar to the benzene ring. Relative intensity measurements prove that the anti form is the global minimum, about 2.0(5) kJ mol(-1) lower in energy with respect to the syn conformer, solving the contrasting results supplied by different theoretical methods. For both conformers, the barriers to internal rotation of the propenyl -CH3 group are low enough to generate fully resolved A-E splittings of the rotational transitions. The corresponding V3 barriers have been determined to be 7.080(5) and 6.978(4) kJ mol(-1), respectively.
authors.affiliation: Dipartimento di Chimica "G. Ciamician" dell'Università , Via Selmi 2, I-40126 Bologna, Italy.
authors.forename: Camilla
authors.initials: C
authors.lastname: Calabrese
authors.affiliation: Dipartimento di Chimica "G. Ciamician" dell'Università , Via Selmi 2, I-40126 Bologna, Italy.
authors.forename: Qian
authors.initials: Q
authors.lastname: Gou
authors.affiliation: Dipartimento di Chimica "G. Ciamician" dell'Università , Via Selmi 2, I-40126 Bologna, Italy.
authors.forename: Assimo
authors.initials: A
authors.lastname: Maris
authors.affiliation: Dipartimento di Chimica "G. Ciamician" dell'Università , Via Selmi 2, I-40126 Bologna, Italy.
authors.forename: Sonia
authors.initials: S
authors.lastname: Melandri
authors.affiliation: Dipartimento di Chimica "G. Ciamician" dell'Università , Via Selmi 2, I-40126 Bologna, Italy.
authors.forename: Walther
authors.initials: W
authors.lastname: Caminati
mesh_terms: D000081248:Allylbenzene Derivatives; D000840:Anisoles / Q000737:chemistry*; D008968:Molecular Conformation; D013055:Spectrophotometry, Infrared; D013237:Stereoisomerism; D013816:Thermodynamics
chemical_list: D000081248:Allylbenzene Derivatives; D000840:Anisoles; C006578:anethole