title: Quantum chemistry studies of far-infrared spectra of aromatic urethanes.
abstract: Restricted Hartree-Fock and density function calculations (B3LYP), using 6-311++G(d,p), have been used to investigate the far infrared spectra of aromatic urethanes, synthesized on the basis of 2,4-and 2,6-toluene diisocyanate (2,4-TDI, 2,6-TDI), and the spectrum of ethylphenylurethane. It is shown, that the region of frequencies of 100-200 cm(-1) is associated primarily with torsional vibrations of methyl groups. For almost all studied urethanes, the bands are observed in the region 385-340 cm(-1), which is associated with in plane deformations of angles C-C-N-C, C-O-C and C-N-C of the urethane groups according to the calculations. The bands, observed at 300-320 and 260-280 cm(-1), are assigned to in plane and out of plane deformations of the urethane skeleton, which are mixed with vibrations of methyl group connected to the benzene ring.
authors.affiliation: Kazan State Architect and Civil Engineering University, Zelenaya, 1, Kazan 420043, Russia. Maklakov_Lev@mail.ru
authors.forename: L I
authors.initials: LI
authors.lastname: Maklakov
authors.forename: G G
authors.initials: GG
authors.lastname: Suchkova
mesh_terms: D002244:Carbon / Q000737:chemistry; D008956:Models, Chemical; D008968:Molecular Conformation; D009584:Nitrogen / Q000737:chemistry; D010100:Oxygen / Q000737:chemistry; D011789:Quantum Theory; D013055:Spectrophotometry, Infrared / Q000379:methods*; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods; D013696:Temperature; D014051:Toluene 2,4-Diisocyanate / Q000737:chemistry; D014520:Urethane / Q000737:chemistry*
chemical_list: D014051:Toluene 2,4-Diisocyanate; D014520:Urethane; D002244:Carbon; C026942:2,6-diisocyanatotoluene; D009584:Nitrogen; D010100:Oxygen