Intramolecular absorption features

Recent advances in spectroscopic methods have enabled the water pentamer to be studied experimentally. Infrared cavity ringdown spectroscopy has been used to examine the intramolecular absorption features of the gas-phase water pentamer, which match the spectral features of the pentamer rings in liquid water and amorphous ice (Paul et al., 1999 Burnham et al., 2002). Vibration Rotation Tunnelling (VRT) spectroscopy has been used to provide a more direct probe of the water pentamer intermolecular vibrations and fine structure in liquid water (Liu et al., 1997 Harker et al., 2005). The water pentamer was found to average out... 

The 10,11-epoxide of chlorovulone I (107) was also obtained in low yield (0.05%) from the hexane extract of C. viridis [124], Its structure was assembled from spectroscopic data which showed a high degree of similarity to that obtained for chlorovulone I (100) except for UV and 1H NMR features due to the Cl0,11-olefin. Confirmation of structure came from synthesis of 107 by epoxidation of chlorovulone I. Epoxy-chlorovulone I (107) was found to possess the same 12R hydroxyl stereochemistry. The cis relationship of the epoxide and hydroxyl group was indicated by an intramolecular hydrogen bond as revealed by characteristic IR absorptions at high dilution. This 10,11-epoxide derivative... 

As was noted in Ref. 29, the absorption in the IR region in alcohols and other polar liquids has the same characteristic features as in water. So in such liquids the IR losses due to excitation of intramolecular vibrations usually must give a crucial contribution to retardation of electrons. If in hydrogen-containing substances the retardation time depends on those intramolecular vibrations for which the reduced mass is determined by hydrogen atoms, there must exist an isotopic effect. 

The vibrations within a molecular crystal cell are not only a result of molecular motions, but also the relative motions between neighboring molecules. Dominant features of the THz spectra are the sharp absorption peaks caused by phonon modes directly related to the crystalline structure [14], This result originates from the molecular vibrational modes and intramolecular vibrations associated, for example, with RDX [39], Consequently, vibrational modes are unique and distinctive feature of the crystalline explosive materials. The presence of broad features might also be caused by scattering from a structure with dimensions comparable to the THz wavelength. This can occur in materials that contain fibers or grains [37],... 

The [TcO]3+ core is sufficiently electron deficient to deprotonate secondary aliphatic amines, and in 36 and analogs neutrality is achieved by loss of both amine protons and one oxime proton, with the remaining oxime proton being intramolecularly hydrogen bonded. Features of the structures are Tc=0 bond distances in the range 1.670(4)-1.682(5) A and the displacement of Tc above the N4 plane, which for 36 is 0.678(1) A. Also, for 36 the distance between Tc and the deprotonated N (imino) atoms of 1.913 A (av.) is considerably shorter than the Tc-N(oxime) distance of 2.090 A (av.) (453). The y(TcO) IR absorption in the rather... 

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