Infrared spectroscopy frequencies Appendix

Adsorption of 0.05 monolayers (ML) of CO on this surface gives rise to a peak at 2015 cm-1 corresponding to the internal C-0 stretch frequency of the molecule in the on-top adsorption site and one at 470 cm-1 due to the metal-molecule bond. The latter is not easily observable in infrared spectroscopy. Increasing the CO coverage to 0.33 ML enhances the intensity of the HREELS peaks. In addition, the C-O stretch frequency shifts upward because of dipole-dipole coupling [16, 17]. The LEED pattern corresponds to an ordered (V3xV3)R30° overlayer in Wood s notation (see the Appendix) in accordance with the coverage of 0.33 ML. 

It may seem there are too many numbers to memorize in infrared spectroscopy. Hundreds of characteristic absorptions for different kinds of compounds are listed in Appendix 2. Please glance at Appendix 2, and note that Appendix 2A is organized visually, while Appendix 2B is organized by functional groups. For everyday use, we can get by with only a few stretching frequencies, shown in Table 12-2. When using this table, remember... 

Different types of carbonyl groups give characteristic strong absorptions at different positions in the infrared spectrum. As a result, infrared spectroscopy is often the best method to detect and differentiate these carboxylic acid derivatives. Table 21-3 summarizes the characteristic IR absorptions of carbonyl functional groups. As in Chapter 12, we are using about 1710 cm-1 for simple ketones and acids as a standard for comparison. Appendix 2 gives a more complete table of characteristic IR frequencies. 

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