Phenol- Water , 1 n 4 Complexes

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 

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), 

a value above the iuequality sign indicates the corresponding frequency difference in cm between its left- and right-hand side quantities. Notice that the first difference Av = Vqh — r i is 48 cm . 

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