Carbon-hydrogen infrared absorption frequencies

For catalysts that were simply dried in air at 110°C after impregnation of the alumina with H2PtClfe and Re207, it was concluded that a platinum-rhenium alloy formed on reduction. This conclusion was based on the observation that the presence of platinum accelerated the reduction of oxygen chemisorbed on the rhenium and on results showing that the frequencies of the infrared absorption bands of carbon monoxide adsorbed on platinum and rhenium sites in platinum-rhenium catalysts were different from those found with catalysts containing only platinum or rhenium. However, for catalysts calcined in air at 500°C prior to reduction in hydrogen, it was concluded that the platinum exhibited much less interaction with the rhenium (66,71). 

A. Pozefsky and N. D. Coggeshall, Infrared Absorption Studies of Carbon-Hydrogen Stretching Frequencies—In Sulfurized and Oxygenated Materials, AnaU Chem. 23, 1611, 1951. 

The infrared spectra of a number of hydroxyalkylmetallocenes have been interpreted in terms of hydrogen bonding involving the metal atom. The best example is provided by the epimeric alcohols (XVI and XVII), which exhibit absorption at 3610 and 3561 cm. , respectively, in dilute carbon disulfide solution 23, 24, 59), The low frequency band which, with the absorption near 3600 cm. appears as well in the spectra of acyclic a- and jS-hydroxyalkylferrocenes, has been assigned to the metal-bound hydrogen bond 23, 24, 59, 61),... 

The absorption infrared spectra of ABA (n = 1-9) and nAOBA (n = 3-12) have been measured in the spectral range from 100 to 4000 cm ( 3 cm-1) and in the temperature interval from 100 to 550 K ( 1 K) [57,58,60]. The assignment of the spectral infrared bands to the vibrations of atoms of the dimer ring (Fig. 2) has been made based on calculations of frequencies and shapes of normal coordinates performed for dimers of homologies of carbon acids [292]. Vibrations of the parareplaced benzoic acid and its alkyl radical have been interpreted on the basis of calculations carried out in Refs. 294 and 295, respectively. The maxima recorded at 2900 cm-1 (Voh band), 1692 cm-1 (vc=o band), and 940 cm-1 (p0H band) for all phases of the ABA and AOBA are direct evidence for the connection of molecules ABA and AOBA via hydrogen bonds. 

Examples of these infrared bands are seen in Fig. 8.7. The first two rows of spectra illustrate benzene rings with alkane substituents. For these, the adjacent hydrogen wag bands tend to increase in frequency somewhat as the a carbon of the substituent is more highly substituted. We can note absorptions for toluene at 728 cm ethylbenzene at 745 cm isopropylbenzene at 759 cm and /ert-butylbenzene at 763 cm ... 

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