Phenols OH stretchings

B 3000 cm -3500 cm Phenolic OH stretch Very broad due to strong hydrogen bonding and thus obscures other bands in this region... 

The infrared (IR) and Raman UV double-resonance spectroscopy of Ph0H(H20) 4 in the OH-stretching vibration region was also smdied . These smdies led to the conclusion that, on the one hand, the symmetric water vj and phenolic OH-stretching (voe) vibrations are downshifted considerably upon the formation of phenol-water complexes (compared with those inherent for bare water and phenol molecules). On the other hand, the antisymmetric V3 vibration of the water molecule is only weakly affected. This results in the appearance of a transparent window region ° in the IR spectrum... 

The IR spectra obtained in dilute CCI4 solutions were similar for nahcolite and trona oils. Several weak bands were noted (Figure 7). Water, 3700 cm-1and a phenolic OH stretching frequency at 3605 cm-1were most obvious. 

Vibrational spectra obtained by electron energy-loss spectroscopy (EELS) of LD adsorbed at Pt(lll) were as shown in Figure 4A. Also shown in the Figure are the locations and relative intensities of bands in the mid-infrared spectrum of solid LD in KBr. The EELS spectra contain peaks corresponding to most of the IR bands of solid LD, although not all of the bands are resolved, and absence of the phenolic OH stretches is to be expected (see catechol, below). Table 3. Shown for comparison are the EELS spectra of the amino acids L-tyrosine (TYR), L-cysteine (CYS), phenylalanine (PHE) and alanine, and of the related compounds dopamine (DA) and... 

Morterra and Low109,110 proposed that thermal crosslinking may occur between 300°C and 500°C where phenolic hydroxyl groups react with methylene linkages to eliminate water (Fig. 7.43). Evidence for this mechanism is provided by IR spectra which show decreased OH stretches and bending absorptions as well as increased complexity of the aliphatic CH stretch patterns in this temperature range. 

T. Ebata, T. Walanabe, and N. Mikami, Evidence for the cyclic form of phenol trimer Vibrational spectroscopy of the OH stretching vibrations of jet cooled phenol dimer and... 

Substraction spectra were obtained by setting the aliphatic C-H stretching band at 2969 cm l at about zero. The spectrum comparing AO/60 PHBA/diol polyol and unmodified polyester (Fig. 3) is typical. The aliphatic OH band at about 3535 cm"l has been largely replaced by a phenolic OH band at about 3365 cm"l. Subtraction spectra of the other oligomers (Fig. A) yield similar conclusions. 

Figure 3.32 PE profiles of the electronic ground state (circles), the lowest 1 tttt state (squares) and the lowest1 mr state (triangles) of phenol as a function of the OH stretching coordinate, calculated with the CASPT2 method [32].

After treatment of Fraction A with anion-exchange resin, the non-reactive portion, acid-free fraction (B), did not exhibit absorptions characteristic of either phenolic OHor acidic NH stretching approximately at 3,600 and 3,480 cm, respectively. This indicates that compounds containing not only phenolic OH group but also acidic NH group can be removed by the reaction with anion-exchange resin, as has been suggested by Scheppele et al. (10). 600 MHz NMR spectra of the... 

A four-parameter equation for predicting the calorimetric enthalpies of acid-base interactions, —Ai/ab, in neutral solvents, proposed by Drago et al. [146], with spectroscopically determined shifts of the OH stretching frequency of phenol when interacting with a variety of bases of dilute solutions in carbon tetrachloride and tetrachloroethylene. 

EELS spectra of the adsorbed layers formed from HQ or BQ solutions were very similar [Figs. 42(a) and (b)], indicating formation of a common horizontally oriented adsorbed state. Also shown in Fig. 42 are the locations of the principal mid-IR bands of solid HQ and BQ. The virtual absence of the OH stretches (3260 cm1) from the EELS spectra of adsorbed layers formed at HQ concentrations below 1 mM indicates that the phenolic hydrogens are lost during adsorption [eqn. (33)]. 

Both alcohols and phenols show -OH stretches in the region 3300-3600 cm-1. 

Aryl substituents in either the 2- or 2,6-position cause a downfield shift of the OH stretching frequency in CCI due to the formation of an intramolecular hydrogen bond to the aromatic ring 170) (phenol 3605 cm-1, 2-phenylphenol and 2,6-diphenyl-phenol 3555 cm "1 2,4,6-triphenylphenol 3553 cm-1). Under the same conditions t-butyl-phenols give rise to higher frequencies (2,6-di-t-butylphenol and 2,4,6-tri-t-butylphenol 3645 cm-1, compared with phenol 3612 cm-1)171). 

We know already that the chosen computational methods accurately describe the properties of pheuol, particularly its vibrational spectrum. The frequeucies of the OH stretchiug vibrations of phenol and water molecule are collected in Table 35. It is interesting to note that the HF/A frequency of 4118 cm" assigned to the vqh stretching vibration of bare phenol corresponds to its highest frequency. Therefore, it can be treated as the most accepting mode of phenol. Moreover, this frequency lies between the frequencies of the vi (4070 cm" ) and (4188 cm" ) OH-stretching vibrational modes of water molecules (equation 40),... 

TABLE 35. The OH-stretching frequencies (in cm ) of water and phenol, and phenol-wateri 2 complexes calculated via the HF/A and MP2/A (in parentheses) computational methods. Infrared intensity is in kmmol , Raman (R) activity in A amu ... 

Five calculated OH-stretching vibrations of the PhOH-W2-l structure are presented in Table 35. By analogy with the PhOH-wi-l complex, the hydrogen-bonded phenolic vqh vibration is red-shifted significantly by 202 cm and its IR intensity is enhanced by a factor of 4.9 while its Raman activity only doubles. The other four vibrations are simply assigned to the vj and V3 of water molecules Wadi and Wadi, although their collective nature (essential for larger water clusters) should be noted. One pair of them, v and... 

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