O-H stretching bands

Prosser, Stuart Wilson (1979) and Prosser, Groffman Wilson (1982) examined the setting of a number of these cements using infrared spectroscopy. The infrared spectrum of the alkyl salicylates showed an O-H stretch band at 3190 cm" and a C-O stretch band at 1675-95 cm" . 

A relationship has been developed that relates the position of the O-H stretching band of an alcohol to the electronic character of the solvent. That equation is based on the assumption that an oscillating... 

There have been many studies on the formation of hydrogen bonds between alcohols and a wide range of bases. If the bases are of similar type (for example, all nitrogen donor atoms in amines), there is also frequently a rather good correlation between the shift of the O-H stretching band and other properties. For example, stretching frequency shifts of the OH bonds in alcohols have been correlated... 

In a certain solvent (A), the O-H stretching band of methanol is observed at 3642cm-1. In that solvent, the heat of reaction of methanol with pyridine is -36.4 kl mol-1. In another solvent (B), the O-H stretching band is observed at 3620 cm-1 and the heat of reaction with pyridine is —31.8kJ mol-1. 

For organic hydrogen bonds, methanol takes the role that HF has for inorganic hydrogen bonds it is the simplest conceivable prototype. Its cluster spectroscopy has been reviewed together with that of water clusters [98], While the monomer vibrational dynamics is in general well-studied [214 217], different values for the fundamental O—H stretching band center are in use [63, 64, 75, 173, 189, 218]. Based on combined Raman and IR evidence, a value of 3684 3686 cm 1 appears well-justified [16, 65, 77, 82, 216]. It serves as an important reference for vibrational red shifts in methanol clusters. 

O—H stretching bands of larger methanol clusters start to overlap. Investigations on their dynamics and isomerism [160, 196, 197] typically require size-resolved studies [174]. The recently proposed size-specific VUV-IR technique is not practical for this purpose, because it produces strongly broadened, spectrally shifted and most likely fragmentation-affected bands for methanol trimer and larger clusters [172]. 

Beyond ethanol, the number of ft-alkanol dimer conformations becomes too large to be vibrationally resolved, even in supersonic jets. For -propanol, more than five isomers are discernible in the donor O—H stretching spectrum (see Fig. 8). For longer chains, there is a smaller number of dominant conformations [69]. Ar relaxation shows that the most stable -propanol and n-butanol dimers are those with the largest observed red shifts. For longer chains, the situation is more complex. However, the window of observed O—H stretching bands is quite independent of chain length beyond propanol. 

Shearken (1968) adopted a modified method of assay by using chloroform as an extracting medium, but instead of the carbonyl band measured the N—H stretching band at 3436 cm-1. However, this particular method essentially requires the complete removal of both water and ethanol the latter is present in CHC13 as a stabilizer which is required to be eliminated completely to avoid interference from O—H stretching bands. To achieve this objective activated alumina columns have been used extensively. However, Zappala and Post... 

At each temperature, the equilibrium concentration of the product was obtained as the difference between the initial and the equilibrium concentrations of phenol, respectively, [PhOH]0 and [PhOH], The latter was determined from the maximum absorbance of the free O-H stretching band. A similar method was used to evaluate the equilibrium concentration of the acceptor acetonitrile, [CH3CN], which is given by the difference between the initial concentration of this acceptor, [CH3CN]0, and the concentration of the product, obtained before. In summary, the equilibrium constant can be represented by equation 14.7 ... 

The conversion of a carboxylic acid to a salt can serve as confirmation of the acid structure. This is conveniently done by the addition of a tertiary aliphatic amine, such as triethylamine, to a solution of the carboxylic acid in chloroform (no reaction occurs in CC14). The carboxylate ion thus formed shows the two characteristic carbonyl absorption bands in addition to an ammonium band in the 2700-2200 cm-1 region. The O—H stretching band, of course, disappears. The spectrum of ammonium benzoate, Figure 3.24, demonstrates most of these features. 

Fermi resonances of the v0H=l state with over- and combination tones of modes in the fingerprint region are considered a key element determining the spectral envelope of the O-H stretching bands of cyclic carboxylic acid dimers. In principle, such Fermi resonances open up channels for population relaxation of the O-H stretching modes through the O-H bending... 

Infrared Spectroscopy. The following bands are seen in the ir spectrum of PPG 2970, 2940, 2880 cm-1 (C—H stretch, m) 1460,1375 cm-1 (C—H bend, m) 1100,1015 cm-1 (C—O stretch, m) of which the 2940 and 1015 band are specific. The latter are also present in copolymers of EO and PO. Absorptions due to unsaturated end groups are found at 1650 cm-1 (allyl ether) and 1672 cm-1 (1-propenyl ether). The O—H stretching band at 3470 cm-1 shows the greatest variation for different hydroxyl number polyols and has been used to estimate the hydroxyl number (169). 

Further spectroscopic characterization of this compound was made using an isotope-labeling technique [71]. In the reaction of H02 with DCDO, the two O—H stretching bands were shifted only slightly to 3558.8 and 3649.2 cm 1, while the C—H stretching band was replaced by a C—D stretching band at about 2200 cm 1. These results further support the... 

Examination of dilute solutions of simple alcohols or phenols in a non-polar solvent such as carbon tetrachloride reveals the free O—H stretching band in... 

The presence of two O—H stretching bands shows that there are at least two types of OH groups on the montmorillonite. Work which will be discussed later shows that interpretation of the spectra of the OH stretching bands is more complicated than would be expected. On the simplest basis the OH bands can be separated into those due to adsorbed water and those due to surface OH groups. These species can be distinguished in cases where it is possible to scan the spectral region past 6.2 p. Adsorbed water... 

---