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1Author    B. Pankoke, K.M T Yamada, G. WinnewisserRequires cookie*
 Title    High Resolution IR-Spectra of Furane and Thiophene  
 Abstract    The spectra of the out-of-plane fundamental band of furane (C 4 H 4 0) centered at 744 cm ~ 1 and of thiophene (C 4 H 4 S) at 712 cm -1 were measured in Doppler-limited resolution with a diode-laser spectrometer at Köln and with a high-resolution Fourier transform spectrometer at the University of Gießen. An interactive Loomis-Wood program was applied to identify the c-type transitions of furane and thiophene. The molecular parameters were determined from the observed line positions and the available microwave data by least-squares-fits using Watson's ^-reduced Hamiltonian. Some relations among parameters appearing in different formulations of the Hamiltonian are represented explicitly in connection with the derivation of the unreduced constants. The unreduced constants were derived for both molecules using the planarity relations. We determined the inertial defects to be « 0.05 amuÄ 2 in the ground state and « —0.2 amuÄ 2 in the excited state for both furane and thiophene. 
  Reference    Z. Naturforsch. 48a, 1193—1202 (1993); received October 4 1993 
  Published    1993 
  Keywords    FTIR, Infrared spectra, Furane, Thiophene, Inertial defect 
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 TEI-XML for    default:Reihe_A/48/ZNA-1993-48a-1193.pdf 
 Identifier    ZNA-1993-48a-1193 
 Volume    48 
2Author    PaavoH. HynninenRequires cookie*
 Title    Electron Donor-Acceptor Properties of 10(S)-Chlorophyll a  
 Abstract    Evidence for the self-aggregation o f 10(S)-chlorophyll a (= chlorophyll a') in nonpolar solvents has been obtained by means o f absorption spectroscopy in the visible and infrared regions. The visible absorption spectrum of chlorophyll a' exhibits a shoulder at 680 nm in aliphatic hydrocar­ bon solvents and the infrared spectrum measured in carbon tetrachloride contains an "aggrega­ tion peak" at 1650 cm "1. IR spectroscopy shows, in addition, that the C-10 epim ers o f chlorophyll a are both present as monom ers in tetrahydrofuran. H ow ever, in the presence of a small amount o f aliphatic alcohol or water, the IR spectrum in tetrahydrofuran at lowered tem peratures exhibits an intense, wide absorption band at ~ 1650 cm -1 which was interpreted as arising from the hydrogen bonding o f the hydroxyl group to the C-9 keto carbonyl o f the chlorophyll. 
  Reference    Z. Naturforsch. 39b, 675 (1984); received July 12 1983 
  Published    1984 
  Keywords    Chlorophyll Epim ers, Chlorophyll Organization, Stereochem istry, Photosynthesis, Infrared Spectra, Absorption Spectra 
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 TEI-XML for    default:Reihe_B/39/ZNB-1984-39b-0675.pdf 
 Identifier    ZNB-1984-39b-0675 
 Volume    39 
3Author    HeinzDieter Lutz, Thomas Kellersohn, Konrad BeckenkampRequires cookie*
 Title    Zur Kenntnis der Hydroxidhalogenide des Bariums  
 Abstract    Kristallstruktur und Schwingungsspektren von Ba[0(H,D)]X • 2 (H ,D)20 (X = CI, Br) Barium Hydroxide Halides. Crystal Structure and Vibrational Spectra of Ba[0(H ,D)]X-2(H ,D)20 (X = Cl, Br) a (0 H)2-B aX 2 -H 20 (X = CI. Br) The quaternary systems B a(O H)2—BaCl2—H 20 and B a(O H)2—BaBr2—H 20 were studied with the help of X-ray and neutron diffraction as well as IR , Raman, D T A , and TG methods. The following compounds have been established or confirmed: B a(O H)Cl hH 20 (n = 0, 1/2, 2) and B a (0 H)B r-«H 20 (n = 0, 1/2, 2). The crystal structures (of hitherto unknown structure type) of B a (0 H)C l-2 H :0 and B a (0 D)C l-2 D 20 were determined by single crystal X-ray methods and neutron powder diffraction (space group P4Inmm, Z = 2, 621 unique reflections, R — 8 . 8 and 1.9%, respectively). Whereas the hydroxide ion in this layer structured compound is non-hydrogen bonded, i.e. no H-bond donor group, nor it is bound to the Ba:+ ions, the water molecules are involved in strong H-bonds to adjacent O H " ions. The coordination of the barium ions is monocapped tetragonal antiprismatic (4 H 20 and 5 halide ions). The IR and Raman spectra of B a (0 H)X -2 H :0 (X = Cl. Br) are assigned and discussed in terms of hydrogen bonding, isotopic shifts, and intermolecular coupling of the bands observed. The stretching modes of the O H " ions (3672 and 3667 cm-1, 95 K) are shifted to higher wavenumbers by about 100 cm"' as compared with those of free O H -ions. 
  Reference    Z. Naturforsch. 44b, 928 (1989); eingegangen am 6. Februar/7. April 1989 
  Published    1989 
  Keywords    Crystal Structure, Barium Hydroxide Halides, Infrared Spectra, Raman Spectra, System: B 
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 TEI-XML for    default:Reihe_B/44/ZNB-1989-44b-0928.pdf 
 Identifier    ZNB-1989-44b-0928 
 Volume    44 
4Author    MaciejJ. Nowak, Krystyna Szczepaniak, Andrzej Barski, David ShugarRequires cookie*
 Title    Spectroscopic Studies on Vapour Phase Tautomerism of Natural Bases Found in Nucleic Acids  
 Abstract    Infrared absorption spectra, in the vapour phase, have been recorded in the regions of NH, OH and carbonyl stretching frequencies, for a series of 1-substituted uracils and 9-substituted adenine and hypoxanthine, form al analogues of the natural nucleosides of uracil, adenine and hypoxanthine found in DNA and/or RNA. A num ber of related analogues was also examined, including the N-methyl derivatives of the known mutagen and chem otherapeutic agent, 5-flu-orouracil. The infrared absorption spectra provide unequivocal evidence for the existence of 1 -substituted uracils as the 2,4-diketo tautom er, of 9-substituted hypoxanthine as the 6 -keto tautom er, and of 9-substituted adenine as the 6 -amino tautomer. These are the known predom inant tautom eric forms in solution, so that the gas phase results are in sharp contrast with those for other nitrogen heterocycles, where the tautom eric equilibrium constants may differ by several orders of m agnitude in going from solution to the vapour phase. The significance of these results is evaluated in relation to the types of heterocyclic bases found in natural nucleic acids, and to concepts of spontaneous and induced m utations in term s of mis-pairing. The ultraviolet absorption spectra of the various compounds have also been exam ined in the gas phase, but proved of relatively lim ited use in studies on tautom eric equilibria under these conditions. Heats of vaporization have been determined for most of the compounds exam ined. In particular the heat of vaporization for 1,3-dimethyluracil, which is incapable of association by hydrogen bonding in the condensed phase, is much lower than for uracil and 1 (3) -m ethyluracils which can associate by hydrogen bonding. 
  Reference    Z. Naturforsch. 33c, 876 (1978); received July 3 1978 
  Published    1978 
  Keywords    N atural Purines and Pyrim idines, Infrared Spectra, Ultraviolet Spectra, Gas Phase Tautom erism, H eats of Vaporization 
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 TEI-XML for    default:Reihe_C/33/ZNC-1978-33c-0876.pdf 
 Identifier    ZNC-1978-33c-0876 
 Volume    33