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Theoretical Investigation of Hydrogen Bonding Effects on Acidity Enhancement of Alkyl sulfonic Acids and Hydroxy Alkyl Sulfonic Acids in Gas and Solution Phase

Najdian, Atena | 2013

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 45207 (03)
  4. University: Sharif University of Technology
  5. Department: Chemistry
  6. Advisor(s): Fattahi, Ali Reza; Hormozi-Nezhad, Mohammad Reza
  7. Abstract:
  8. Hydrogen bonding is an important weak interaction encountered in gas, liquid, as well as solid phases. The hydrogen bond plays a very vital role in many life processes and is one of the most frequently used terms in chemistry and biology.
    Polyols or polyhydric alcohols are, strictly speaking, simply organic chemicals containing more than two hydroxyl groups. Each hydroxyl is attached to separate carbon atoms of an aliphatic skeleton.They may also contain ester, ether, amide, acrylic, metal, metalloid and other functionalities; along with hydroxyl groups. Polyols are obtained from many plant and animal sources and are synthesized by a variety of methods. Among important properties of polyols, acidity is remarkable due to the role of cooperativity of intramolecular hydrogen bonds in acidity enhancement of polyols.
    The goal of this project is to investigate the acidity of alkyl sulfonic acid by changing some parameters include the size of alkyl chain, adding hydroxyl group to create polyol of alkyl sulfonic acids and the last parameters is the position of hydroxyl group and its influenses on acidity of monohydroxy alkyl sulfonic acids. All the gas phase optimizations and energy calculations were performed at the DFT/B3LYP/6-311++G(d,p) level of density functional theory (DFT) calculations. The solution phase calculations were performed in the water, dimethyl sulfoxide and acetonitrile solution as a commonly used solvents in organic reactions. Also, in order to study the nature of effective bonds in interactions, QTAIM and NBO analyses are used. As expected, cooperativity of hydrogen bonds in these models shows drastic influence in acidities of these molecules. Linear correlation between gas phase acidity (GPA) and pka in solution phase for model poly hydroxyl alkyl sulfonic acids can be used for prediction of pka for other alcoholic models
  9. Keywords:
  10. Acidity ; Atom in Molecule Method ; Natural Bond Orbital (NBO) ; Alkyl Sulfonic Acid ; Cooperative Hydrogen Bond

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