Vibrational energy carboxylic acids

Figure 2.4 Carboxylic acid dimer in the potential energy minima with local vibrational states. OV represents the correlation time for a thermally activated proton transfer, and TU, the correlation time for tunneling transfer. (Reproduced with permission from ref. 29.)...

The IR spectra of hydroxy adds are not very different from the spectra of the corresponding carboxylic acids. The additional hydroxyl groups usually produce minor displacements of the carbonyl vibrational bands to higher energies and, of course, contribute additional characteristic... 

Solvation free energies can be used to evaluate conformational preferences, energy minima and reaction profiles for any chemical system in solution of course the quality of the results depends also on the level of the theoretical approach (i. e. on the calculation in vacuo), but in many cases one can say that the inclusion of solvent effects does not lower the performances of the overall description. In this framework, it is very useful to evaluate the solvent effects on the solute geometry (this is sometimes called indirect solvent effect), and also on the vibrational frequencies (adding zero point energy corrections to the calculated free energies) as briefly sketched above, PCM is able to compute both geometry and vibrational corrections effectively. Recently PCM has been used for the ab initio prediction of the pKa of a number of carboxylic acids[111] ... 

It has been shown that the isotope effects on the acidities of a series of carboxylic acids and 3,5-difluorophenol originate only in changes in vibrational frequencies and zero-point energies upon deprotonation. No evidence for an inductive contribution or electron-donation effect was found. 

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