Infrared stretching frequency

A variety of instmments are available to analyze carbon monoxide in gas streams from 1 ppm to 90%. One group of analyzers determines the concentration of carbon monoxide by measuring the intensity of its infrared stretching frequency at 2143 cm . Another group measures the oxidation of carbon monoxide to carbon dioxide electrochemically. Such instmments are generally lightweight and weU suited to appHcations requiring portable analyzers. Many analyzers are equipped with alarms and serve as work area monitors. 

The relative electron-donating ability of rings can be estimated by the change in the infrared stretching frequencies of attached amino, carbonyl, cyano, or methoxy groups, but the quantitative relation to chemical reactivity does not appear to be defined at... 

Triphenylphosphine selenide crystallizes from absolute ethanol as small white needles which melt at 187 to 188°. The compound is very soluble in dichloromethane moderately soluble in hot methanol, hot ethanol, hot acetonitrile, hot benzene, and hot 1-butanol and insoluble in ether and water. The PSe infrared stretching frequency occurs at 562 cm.-1 (Nujol mull). 

Figure 3.15 Infrared stretching frequencies (Adapted from Sandford 1996)...

The infrared stretching frequency of the hydroxyl associated with the Bronsted sites in decationized zeolites, fails in the range 3600 to 3660 cm. As the Si/Al ratio in the framework increases, this frequency tends to decrease. What does this suggest about the acidity of the highly siliceous zeolites ... 

Tcblc 18.2 Infrared stretching frequencies of some phosphoryl compounds... 

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. 

Infrared vibrational energies of ligating groups such as CO, N2, NO or RNC (R = alkyl or aryl) have been extensively correlated with redox potential data.28 37""41 For a series of closely related mononuclear complexes it is generally observed that as E° (or EVl) for the oxidation of members of the series becomes increasingly positive, then v, the infrared stretching frequency for the (ter-... 

One of tire distinguishing physical characteristics of the cephalosporins is the infrared stretching frequency of the /i-lactam carbonyl. This absorption occurs at higher frequencies (1770-1815 cm-1) than those of either normal secondary amides (1504-1695 cm-1) or ester carbonyl groups (1720-1780 cm-1). 

Use the infrared stretching frequencies in Table 12.4 to distinguish between different classes of organic compounds. 

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