Ring deformational mode

The structure on the above peaks with a separation of 65 cm -1 arises from a progression in a totally symmetric ring deformation mode. Low frequency modes in the 100-200 cm-1 range of the IR spectrum of Pt(hfacac)2 and Pt(acac)2 have been observed and attributed to ring deformation modes but not completely assigned [36, 37]. 

In the benzene data (49) in Fig. 16, the 606 cm-1 ring deformation mode has a two-part rise. The first part mirrors the 10 ps decay of the C-H stretch. The second part mirrors the 40 ps decay of intermediate energy vibrations such as the ring breathing mode at 992 cm-1. The decay lifetime is difficult to determine accurately because it is so slow, but is estimated at 100 ( 20) ps. 

Gupta et al. have also made a compilation of IR data on 25 pyrrolizidine esters. Peaks at 740-760, 800-950, 960-980, and 1075-1130cm" were assigned to ring deformation modes, and absorptions at 610, 750, and 965 cm" were attributed to the saturated flve-membered ring. 

The far-infrared spectra of free phenanthroline (253, 392) and bi-pyridyl (78, 253, 291, 392, 453, 544) have been examined. In the solid state the spectrum of bipyridyl consists of bands at 625, 430, 405, 164, and 92 cm in chloroform solution (660-222 cm ) this is modified to 616, 401, and 385(sh) cm . Attempts have been made to offer assignments on an empirical basis thus it is reasonably certain that the bands at 625 [a(CCC)-re ] and 405 cm" [< (CC)-viea] are ring-deformation modes. 

O-C-0, C-O-C, C-O-H, and aromatic ring deformation modes), the assignments have proven quite useful. 

Table 4.9 Aromatic C—H Ring Deformation Modes and Benzene Ring Substitution...

The results of these experiments are shown in Figure 9. Of the spectral features apparent in the lgG2a antibody spectram, the most intense band at 1000 cm likely arises from the in-plane ring deformation mode of Phe in IgG (50,51). The amide III protein mode at 1260 cm may be observed in both the IgG and RSV+IgG spectra (52), however, unique, prominent bands are observed in the 1400 - 1600 cm" region, presumably due to selectively enhanced nucleic acid and/or side-chain vibrations (53,54). 

---