Bonds infrared stretching frequency

Complex formation results in a downfield change in the chemical shift of the methyl protons and a decrease in the double-bond infrared stretching frequency from 1680 to 1532 cm h In the presence of a small excess of PdCl2, the complex is rapidly converted to hexamethylbenzene and palladium chloride. 

In Table VII are recorded mean values for in a number of ethylene-metal carbonyl complexes and parent metal carbonyls as well as values for the double-bond infrared stretching frequency rc c the magnetic shielding parameter t for ethylene in those transition metal complexes for which data are available. Although with the metal carbonyl complexes, differences of geometry, oxidation state, etc., do not permit a correlation to be drawn between the absolute values of rco and for the various complexes, it is quite apparent from the tabulated data for the Mo, Mn, and Fe complexes that for a given metal. 

The thioester group (r )[C(=0)-S]) (Scheme 10) can be distinguished from the thionoester (i )[C(=S)—O]) by the carbonyl infrared stretching frequency (-1700 cm-1) and by the absence of the C=S bond (1200-1050 cm-1). In general, thioesters are both more readily synthesized and are more vulnerable to nucleophilic cleavage by virtue of a sulfur leaving group. 

For the detection of subtle differences within a given series of closely related compounds, spectroscopic studies are generally more useful than diffraction studies. An inverse correlation between the C=C bond lengths and the infrared stretching frequencies, vc-c, in a series of ethylene complexes has been observed (63) (Fig. 5A). There is at present some discussion about the nature of the infrared band observed around 1500 cm-1 [(70) and referen3es therein]. It is found that the normal mode contains... 

Table 9 Infrared stretching frequencies for exocyclic double bonds on small rings...

Figure 16 f-LDOS on the clean metal surface and (extrapolated) infrared stretch frequency of CO adsorbed on those same surfaces. The samples are Pt/zeolite with different zeolite acidity. This plot says that the C-0 intramolecular bond after chemisorption will be weaker if the initial clean-surface iif-LDOS is higher. 

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