Exploring of Hydrogen Bond Effect on  Acidity Value for Multifunctional Alcohols in Gas Phase & Nonaqueous Solvent via DFT Method

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Abedin Maghanaki, Azar Dokht | 2010

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Type of Document: M.Sc. Thesis
Language: Farsi
Document No: 41695 (03)
University: Sharif University of Technology
Department: Chemistry
Advisor(s): Fattahi, Alireza
Abstract:
Hydrogen bond is a type of molecular bonds which occurs between hydrogen and a highly electronegative atom( usually F, N and O) and results to special properties. Polyols and multihydroxyl compounds are among substances which have special properties such as acidity due to the existence of hydrogen bond in their molecular structure. Acidity in these compounds is a result of having stable anions due to intramolecular hydrogen bands. The existence of an electronegative group in addition to hydroxyl groups leads to increase the acidity in these substances. In this project acidities of some polyols and multihydroxyl compounds were calculated in both gas phase and solution phase( DMSO, MeCN, THF) using gaussian 2003 software and PCM and also using MP2/6-311++G(d,p)//B3LYP/6-31+G(d) method. As expected, the results showed a drastic increase in these compounds’acidity caused by the existence of hydrogen bond in their molecular structure, and addition of electronegative groups in appropriate sites can result in strengthening their acidity in aprotic solvents and make it as high as carboxylic acids, inorganic and cathionic acids. A new category of strong bronsted acids is introduced in this way.
Keywords:
Nonaqueous Solvents ; Acidity ; Density Functional Theory (DFT) ; Polyol

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