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Evaluation of the halogen bond and the salt bridge interaction using the molecular torsion balance

Keyser, Sandra Kim (2010) Evaluation of the halogen bond and the salt bridge interaction using the molecular torsion balance. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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A molecular torsion balance was synthesized to study the halogen bond in nonpolar and polar solvents. The folding energies were found to be between -0.2 and -0.3 kcal/mol in deuterochloroform. The strength of the halogen bond decreased in the following order: Cl ~ Br > I, which is contrary to the computationally predicted order, I > Br > Cl. This reversed trend may be due to the gauche effect and/or simultaneous steric effects specific to our model system. Three different functionalities, an alcohol, a carbamate, and an amide, were used as the halogen bond acceptors. The amide gave among the highest folding ratios, indicative of the strength of the halogen bond with bromide or chloride. Solvent studies were performed on the brominated torsion balance as well as a hydroxy analog to compare the hydrogen and halogen bonding interactions. Based on the solvent data, it takes more water to obstruct a halogen bond compared to a hydrogen bond. The folding energies were also compared to several solvent parameters. A molecular torsion balance was also successfully synthesized to study the solvent exposed salt bridge interaction in water and in several buffer solutions. We found that the folding energies varied between -0.3 to -0.5 kcal/mol for the ammonium-carboxylate and guanidinium-carboxylate interaction when exposed to solvent; unequivocally, salt bridges that are exposed to solvent are stabilizing. Temperature is negligible whereas ionic strength has a weak but experimentally significant effect on the strength of the salt bridge interaction. The only measurable change in the folding ratios came from adjusting the pD of the buffer solutions.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Keyser, Sandra Kimsyk7@pitt.eduSYK7
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairWilcox, Craig Sdaylite@pitt.eduDAYLITE
Committee MemberGrabowski, Josephjoeg@pitt.eduJOEG
Committee MemberJen-Jacobson, Lindaljen@pitt.eduLJEN
Committee MemberNelson, Scottsgnelson@pitt.eduSGNELSON
Date: 30 September 2010
Date Type: Completion
Defense Date: 13 August 2010
Approval Date: 30 September 2010
Submission Date: 2 August 2010
Access Restriction: 5 year -- Restrict access to University of Pittsburgh for a period of 5 years.
Institution: University of Pittsburgh
Schools and Programs: Dietrich School of Arts and Sciences > Chemistry
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: halogen bond; halogen bonding; noncovalent interactions; salt bridge; torsion balance; weak intermolecular interactions; ion pair; Troger's base
Other ID:, etd-08022010-173238
Date Deposited: 10 Nov 2011 19:56
Last Modified: 15 Nov 2016 13:47


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