C — O, stretching modes

Fig. 1 Infiaied spectra of the C—O stretch mode of different coverages CH3O on Cu(lOO) at 100 K. The large frequency shift is mainly caused by the dipole-dipole interactioa Reproduced by permission from Ryberg. )...

As yet, the only work that has been reported on a single crystalline surface has been done by Hoffmann and Robbins . They used the same approach as Burrows eta/. to study the methanation reaction (CO-I-3H2- CH4 + HjO) on a Ru(001) surface. Figure 21 shows the spectra of the C—O stretch mode taken at 50 torr of a mixture of CO and Hj at temperatures up to 600 K. The decrease in peak height at SOO K indicates the buildup of a passivating carbon layer. The negative absorption around 2140 cm is due to imperfect canceling of the gas phase CO band. 

The vibrational bands of the O-H bending and C-O stretching modes are shown in Fig. 6... 

Compound Geometry Point C—O stretching mode symmetries IR octive modes Observed frequencies (cm-1)... 

SERS due to pyridine on Au electrode surfaces appears to arise from the adsorption of pyridine in or on surface carbon present after the oxidation-reduction cycle [25,26], Anodically roughened Ag electrode surfaces, which were subsequently cathodically cleaned, exhibited no SERS from pyridine. This confirms that the SERS-active phase is carbon-pyridine and not pyridine alone. In ultrahigh vacuum, SERS can be induced in pyridine by coadsorbing pyridine with CO [27], The effect depends on the type of silver surface and involves shifts in the peak positions and intensities of some of the vibrational modes. SERS peaks were not observed at 2100 cm 1 at the position of the C O stretching mode of CO. A possible interpretation is that surface complexes are formed between pyridine and CO molecules at the active or hot sites on the silver surface. 

The C—O stretching mode is coupled with the adjacent C—C stretching vibration thus in primary alcohols the vibration might better be described as an asymmetric C—C—O stretching vibration. The vibrational mode is further complicated by branching and... 

P=0 stretch C—O stretch 1271 1258 Combined doublet at 1250 1205 Both the P=0 and C—O stretching modes were shifted... 

Figure 3.2 FTIR spectra of gaseous CO2, CO, NO and CH4 (IR active fundamental modes) and of CH3OH (C—O stretching mode only).

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