Methane vibrational analysis

Both the Raman and the infrared spectrum yield a partial description of the internal vibrational motion of the molecule in terms of the normal vibrations of the constituent atoms. Neither type of spectrum alone gives a complete description of the pattern of molecular vibration, and, by analysis of the difference between the Raman and the infrared spectrum, additional information about the molecular structure can sometimes be inferred. Physical chemists have made extremely effective use of such comparisons in the elucidation of the finer structural details of small symmetrical molecules, such as methane and benzene. But the mathematical techniques of vibrational analysis are. not yet sufficiently developed to permit the extension of these differential studies to the Raman and infrared spectra of the more complex molecules that constitute the main body of both organic and inorganic chemistry. 

Thermolysis of thietane yields principally ethylene and thio-formaldehyde, a vibrational analysis being done on the latter derived from both protio- and perdeuteriothietane. The kinetics has been studied.Thermolysis of 2-phenylthietane proceeds similarly.A number of other products such as methane, ethane, propane, thiophene, and allyl mercaptan have been observed. 

Irradiation using 0.8 MeV proton irradiation or far-UV photolysis at 10—20K of polar and apolar ices rich in CO2, containing acetylene or methane with analysis by IR, gave evidence for ketene formation, which was proposed to occur by free radical processes. Reagents labeled with and were used in most of the experiments, since the normal ketene asymmetric stretch is nearly coincident with the solid CO fundamental vibration near 2136 cm . A major route for ketene formation from acetylene was assigned to reaction with oxygen atoms (Eqn (4.15)). Acetamide (CH3CONH2) has an abundance in space comparable to that... 

Excited-state Mg atoms react with methane and other alkanes via H atom abstraction in the gas phase (equation 1). By studying the vibrational states of the MgH product, information on the mechanism has been inferred. It has been found that regardless of the alkane, RH (and thus the C—H bond strength), the vibrational state distributions are essentially identical. This suggests that long-lived vibrationaUy excited [RMgH] complexes are not intermediates for equation 1 in the gas phase. The situation is quite different for excited-state Mg atoms reacting with methane under matrix conditions, where the insertion product (equation 2) is sufficiently stable for analysis via infrared spectroscopy ". Calcium atoms have been shown to insert into the C—H bonds of cycloalkanes. ... 

This analysis may be extended to formally achiral molecules that are composed of four or more atoms. The motions in such polyatomic molecules are restricted by the restoring forces imposed by bonding, and stochastic achirality is here the result of internal vibrations. Thus, for example, molecular deformations in some vibrational states impart chirality to the methane molecule, but the sense of chirality averages to zero under the conditions of measurement. As this discussion makes clear, the conventional symmetry of methane is a property solely of the model. 

After exposure to methane the IR spectra of manganese oxide showed absorption bands, which are characteristic of the C-H stretching vibrations (CHs 2962, 2872 cm CH2 2926, 2853 cm and CH 2890 cm ) [9]. The intensity of the C-H bands increased, if the exposure time to methane increased (Figs. 2,3). The intensity of the band at 1050 cm, which is assigned to V3(Si-0) of silica was used as an internal reference (Fig. 2). the intensity ratio for the CH2 and CH3 groups estimated for samples after 30 min reaction with methane, was found to be about five [10]. Thus XPS and FTIR surface analysis showed that carbonaceous material formed on the MnOx catalyst surface consists of CHx hydrocarbon deposits and manganese carbide species. 

Devise a strategy and follow through with further calculations to provide a detailed analysis of the contribution of vibrational motion to Cp. Make one key assumption to simplify your analysis. Assume that all 9n modes of vibration are degenerate for each alkane, and that the nine equal values of for methane are the same as the 18 equal values of 0 for ethane, which, in turn, are the same as the 27 equal values of 0 for propane, and so on. Of course, this assumption is not valid, but it should not interfere much with the thought process. Analyze the empirical temperature polynomials for Cp from a statistical thermodynamic viewpoint. 

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