Vibrational spectra including Raman

Vibrational spectra including Raman data of 3,3-dimethyldiaziridine and its hexadeutero compound were recorded in the gas phase and in the crystalline state. Assuming C2 symmetry and employing isotopic shifts and comparison with azetidine, a classification of bands which regarded 33 normal modes could be given (75SA(A)1509). 

We have used the systems CnH +2 with n = 2,4,...,22, C H +2 with n = 3,5,...,21, and C H +2 with n = 4,6,...,22 to represent pure PA, positively charged solitons, and bipolarons respectively. SCF wavefunctions were calculated with a double-zeta quality basis set (denoted 6-3IG) and optimized geometries for all these systems were determined. In addition for the molecules with n up to 11 or 12 we calculated the vibrational spectrum, including infrared and Raman intensities. 

Complete infrared and Raman data for pyridazine are given and assignments were made. A review by Katritzky and Ambler includes infrared data for pyridazine and other heteroaromatic compounds. Infrared spectroscopy has been applied also to the study of hydrogen-bonded complexes with phenol. Calculations on the vibrational spectrum of pyridazine have been performed. ... 

The vibrational modes of the ground-state phenol were examined by a number of spectroscopic techniques including UV-VIS - , IR for the vapour ", and the IR and Raman spectra in the solid and liquid phases - and microwave spectroscopy ", see also References 164-166. They are collected in Table 8, where both nomenclatures by Wilson and coworkers and VarsanJ i are used. Recently, the vibrational modes of phenol have become a benchmark for testing ab initio and density functional methods " . The Hartree-Fock calculations of the vibrational spectrum of phenol were first performed using the 6-31G(d,p) basis set. An MP2 study with the same basis set was later carried out. A combination" of three methods, viz. HF, MP2 and density functional BLYP, in conjunction with the 6-31G(d,p) basis was used to study the phenol spectrum and to make the complete and clear assignment of its vibrational modes (see Table 9). 

A much larger number of bands is found in the IR-spectrum of C70 because the molecule is less symmetric (Figure 2.28). Again the experimental observations are reflected in theoretical considerations on molecular symmetry. There is a total of 204 vibrational modes, including 122 fundamentals. 13 of these are IR-active, and 53 are Raman-active. 

Optical spectra are labeled as IR (infrared), R (Raman), and UV (electronic spectrum including the visible region). IR bands and Raman lines are given in cm the assigned bands are usually labeled with the symbols v for stretching vibration and 6 for deformation vibration. Intensities occur in parentheses either in the common qualitative terms (s, m, w, vs, etc.) or as numerical relative intensities. The UV absorption maxima, given In... 

IR and Raman spectra have been reported for the radical dianion system (12), for which detailed vibrational assignments, including VasSNS at 919 cm and VsSNS 676 cm- 423 jr spectrum of FC(0)NS(CF3)F2- includes vC=0 bands at 1724 and 1761 cm suggesting the presence of > 1 isomer... 

Most fundamental work on the vibrational spectra of azoles appeared in the period 1960-1980. Examples of more recent work include (i) a complete assignment of the gas-phase IR spectrum of indazole (93JCS(F1)4005) (ii) IR spectral data were used to determine the enthalpies of 0—H. . . N and N—H. . . O bonds in complexes of formic acid and 3,5-dimethylpyrazole (87MI301-01) (iii) the vibrational assignment of the Raman spectrum of polycrystalline pyrazole (92MI301-01) based on 3-21G calculations. 

To date, no Raman spectrum of syndiotactic polypropylene has been published although vibrational analyses have been issued by Schacht-schneider and Snyder and also by Peraldo and Cambini during 1965. Recently we have had the opportunity to examine polypropylene in three forms atactic, isotactic and syndiotactic. The results for the last specimen are included in Fig. 6. It will be seen that there is an enormous emission in the 1350—1400 cm-1 region. The nature of this is not known — it may be fluorescence but it cannot be checked, as the anti-Stokes band at v0+ 1350 cm-1 would be vanishingly weak due to the low Boltzmann population 1350 cm-1 above the ground state. A coordinate analysis is available for syndiotactic polypropylene and currently we are working on an assignment of the observed results. 

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