title: Vibrational normal modes of diazo-dimedone: a comparative study by Fourier infrared/Raman spectroscopies and conformational analysis by MM/QM.
abstract: The 2-diazo-5,5-dimethyl-cyclohexane-1,3-dione (3) was synthesized and the FT-IR/Raman spectra were measured with the purpose of obtain a full assignment of the vibrational modes. Singular aspects concerning the -CNN oscillator are discussed in view of two strong bands observed in the region of 2300-2100 cm(-1) in both, Infrared and Raman spectra. The density functional theory (DFT) was used to obtain the geometrical structure and for assisting in the vibrational assignment joint to the traditional normal coordinate analysis (NCA). The observed wavenumbers at 2145 (IR), 2144(R) are assigned as the coupled nu(NN)+nu(CN) vibrational mode with higher participation of the NN stretching. A 2188 cm(-1) (IR) and at 2186 cm(-1) (R) can be assigned as a overtone of one of nu(CC) normal mode or to a combination band of the fundamentals delta(CCH) found at 1169 cm(-1) and the delta (CCN) found at 1017 cm(-1) enhanced by Fermi resonance.
authors.affiliation: Universidade Federal Fluminense, Departamento de Química Inorgânica, Instituto de Química Campus do Valonguinho s/n, Niterói-Centro, 24210-150 Rio de Janeiro, Brazil. tellez@vm.uff.br
authors.forename: C A
authors.initials: CA
authors.lastname: Téllez Soto
authors.forename: J M
authors.initials: JM
authors.lastname: Ramos
authors.forename: R S
authors.initials: RS
authors.lastname: Rianelli
authors.forename: M C B V
authors.initials: MC
authors.lastname: de Souza
authors.forename: V F
authors.initials: VF
authors.lastname: Ferreira
mesh_terms: D001391:Azo Compounds / Q000737:chemistry*; D003198:Computer Simulation; D003510:Cyclohexanes / Q000737:chemistry*; D008956:Models, Chemical; D008968:Molecular Conformation; D012984:Software; D017550:Spectroscopy, Fourier Transform Infrared; D013059:Spectrum Analysis, Raman; D014732:Vibration
chemical_list: D001391:Azo Compounds; D003510:Cyclohexanes; C506365:Cyclohexane