O—H Bands

A recent review (Murthy and Rao, 1968) has discussed in detail the use of infrared and Raman spectroscopy, as well as NMR and electronic spectroscopy, for studying the hydrogen bond in many types of systems. Infrared spectra are frequently used for the detection of hydrogen bonding, which may be either intermolecular or 

In solution, both penta-O-acetyl-aWe/jydo-D-galactose aldehydrol (XIV) and the corresponding ethyl hemiacetal (XV) display a band (Isbell et al., 1957) at 3597 cm for free hydroxyl, and a band at 3483 cm for hydrogen-bonded hydroxyl. 

Tipson et a/. (1962) examined the O—D bands in the spectra of fully 0-deuterated sugars. The OH band at 3390cm of a,/ -D-glucose was shifted, when deuterated, to 2469 cm a wave number ratio of 1.37, and other new bands appeared. 

The stretching absorption of C=C is weak and has limited diagnostic value symmetrically disubstituted acetylenes do not show it. A weak stretching band for H—C=C—R falls at 2150-2100 cm for example, 5-hexyne-D-lyxo-l,2,3,4-tetrol tetraacetate exhibits a band (Hurd and Jenkins, 1966) at 2150cm and two 6-heptynepentol derivatives have a band (Horton and Tronchet, 1966) at 2120-2110 cm In the case of R—C=C—R, the band lies at 2260-2190 cm  

Phenyl-conjugated C=C bonds have a strong stretching band at 1625 cm in CO or C=C conjugation, the band lies at 1600cm Nonconjugated C=C bonds show bands at 1680-1620 cm For olefins, a cis double bond in RCH=CHR lies at 1662-1653 cm S and a trans double bond at 1678 1653 cm Thus, trans-3-hexene-D-t/irco-l,2,5,6-tetrol has a band (Tipson and Cohen, 1966) at 1653 cm A terminal exocyclic double bond, as in H2C=CRR, displays a band at 1658-1648 cm and H2C=CHR displays one at 1648-1638 cm  

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The N—H functional group of amines is also easy to spot in the IR, with a characteristic absorption in the 3300 to 3500 cm-1 range. Although alcohols absorb in the same range, an N—H absorption is much sharper and less intense than an O-H band. 

Propanal has a medium-sharp stretching band at 2720 cm due to the aldehydic H. Propanoic acid has a very broad O—H band at 2500-3300 cm. The C=0 bands for both are in the same general region, about 1700 cm. ... 

Other than the shift lo lower wavenumber of the C-0 and O-H bands, what other feature of Figure 3.15b indicates increased hydrogen bonding ... 

Addition of Mo to A1203 has been reported to lower and shift the frequency of the Al-O-H band (57, 75). This has been interpreted as due to covering of the A1203 surface by a molybdena layer, or actual loss of OH by interaction during preparation or calcination of the catalyst. The latter view agrees with a suggested reaction put forth by Dufaux et al. (36),... 

Influence of Pressure on the v(Q-H) Region. Upon evacuation of the KH complex, the position of the inner-hydroxyl v(0-H) band at 3620 cm 1 increased in frequency to 3628 cm 1 (Fig. 5c). Therefore, in order to examine more fully the influence of pressure on the v(O-H) bands of the KH complex, IR spectra were collected as a function of pressure (Fig. 6). At 1 atm of pressure, the IR spectrum of the KH complex is similar to the Raman result intensities of the ISu v(O-H) bands are decreased in comparison to those of kaolinite, and the inner-hydroxyl band at 3620 cm 1 is not perturbed. Upon decreasing the pressure, however, a "new" band at 3628 cm 1 grows in intensity at the expense of the 3620 cm 1 band. The 3628 cm 1 band was not observed in the earlier IR studies of the KH complex (12), which were conducted at 1 atm pressure. 

Returning with hindsight to the infrared spectrum, we may note the strong H—C= stretching band at 3294 cm superposed on the O—H band.There is also a strong =C—H band at 640 cm. Furthermore, there is a weak but distinctive C=C stretching band at 2117 cm-1. 

Under 50 mbar of H2 and 50 °C, SnBu4 reacts selectively on the Pt surface to form surface complexes of average formula Pts[SnBux] /. The empirical formula (values of x and y) depend on the reaction time and on the Snint/Pts ratio (Fig. 6). Note that under these conditions SnBu4 does not chemically react with the silica surface, but it is fully physisorbed on the support [114]. In fact, when silica is contacted with SnBu4, IR spectroscopy shows a shift of the v(O-H) band of silica to lower wave numbers, i.e. from 3747 cm to ca. 3700 cm which results from van der Waals interactions between the hydroxyl groups of the support and the butyl chains of adsorbed SnBu4 (Scheme 32). 

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