Bridging-stretching

Force constant calculations for the in-plane vibrations of PtyX /t-X) - show that the terminal stretching force constants are larger than the bridging stretching force constants but that the difference diminishes for the heavier halides.1920... 

The theoretical treatment is limited to the one-dimensional approach. The multidimensional procedure taking into account the coupling of the bridge stretching and bending modes is, at the moment, practically impossible for such large systems as DMAN-s derivatives. 

Most theories of H-bonding have as their starting point the interaction of the fast X-H stretching motion (Vj) and the slow XH. .. Y bridge stretching motion (v3 or v0). This is a useful working hypothesis but a somewhat simplified view. As already stated there are other low frequency H-bond vibrations with which vt can interact. 

As stated above this spacing is about 90-100 cm-1. This should correspond to the v bridge stretching frequency. It has been measured to be 119 cm-1 by Belozerskaya and Shchepkin26). 

For the amines they found NH3 < MeNH2 < Me2NH < Me3N. For the chloroform-amine complexes the Av are 12,26,45 and 53 cm-1 in this order. No subbands were resolved. This is, no doubt, due to the low frequency of the bridge stretching vibration v for these very weakly H-bonded systems and to the weakness of the anharmonic coupling between them. The existence of the molecules in more than one conformation broadens the bands and makes the observation of the subbands even more difficult. 

It may be that the anion in 02 Sb2Fn possesses a linear bridge and that the O2 species are symmetrically placed about the anion. This would account for the absence of features in the Raman spectrum attributable to bridge stretching. In the XeF Sb2Fir and XeF3 Sb2Fu salts... 

These heteropoly salts are all white solids with similar IR spectra and well-resolved medium to strong peaks at 1130-970 cm " (P—O stretch) and 950-890 and 730-660cm (M—O terminal and bridging stretches). The ammonium and tetramethylammonium (sodium double) salts are soluble in water tributylammonium pentatungstobis(phenylphosphonate) is insoluble in water and methanol but soluble in acetonitrile, /V./V-dimethylformamide, dimethyl sulfoxide, and dichloromethane. Proton NMR spectra of the... 

J. R. Carney, A. Fedorov, J. R. Cable, and T. S. Zwier, The infrared spectroscopy of H-bonded bridges stretched across the cw-amide group I. Water bridges, J. Phys. Chem. A 105, 3487-3497 (2001). 

Location of Antifoam Action — Fast and Slow Antifoams Bridging-Stretching Mechanism Role of the Entry Barrier... 

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