eprintid: 8836
rev_number: 5
userid: 6
dir: disk0/00/00/88/36
datestamp: 2011-11-10 19:56:30
lastmod: 2016-11-15 13:47:56
status_changed: 2011-11-10 19:56:30
type: thesis_degree
metadata_visibility: show
contact_email: syk7@pitt.edu
item_issues_count: 0
eprint_status: archive
creators_name: Keyser, Sandra Kim
creators_email: syk7@pitt.edu
creators_id: SYK7
title: Evaluation of the halogen bond and the salt bridge interaction using the molecular torsion balance
ispublished: unpub
divisions: sch_as_chemistry
full_text_status: public
keywords:  halogen bond; halogen bonding; noncovalent interactions; salt bridge; torsion balance; weak intermolecular interactions; ion pair; Troger's base
abstract: 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.
date: 2010-09-30
date_type: completed
institution: University of Pittsburgh
refereed: TRUE
etdcommittee_type: committee_chair
etdcommittee_type: committee_member
etdcommittee_type: committee_member
etdcommittee_type: committee_member
etdcommittee_name: Wilcox, Craig S
etdcommittee_name: Grabowski, Joseph
etdcommittee_name: Jen-Jacobson, Linda
etdcommittee_name: Nelson, Scott
etdcommittee_email: daylite@pitt.edu
etdcommittee_email: joeg@pitt.edu
etdcommittee_email: ljen@pitt.edu
etdcommittee_email: sgnelson@pitt.edu
etdcommittee_id: DAYLITE
etdcommittee_id: JOEG
etdcommittee_id: LJEN
etdcommittee_id: SGNELSON
etd_defense_date: 2010-08-13
etd_approval_date: 2010-09-30
etd_submission_date: 2010-08-02
etd_access_restriction: 5_year
etd_patent_pending: FALSE
assigned_doi: doi:10.5195/pitt.etd.2011.8836
thesis_type: dissertation
degree: PhD
committee: Craig S. Wilcox (daylite@pitt.edu) - Committee Chair
committee: Joseph Grabowski (joeg@pitt.edu) - Committee Member
committee: Linda Jen-Jacobson (ljen@pitt.edu) - Committee Member
committee: Scott Nelson (sgnelson@pitt.edu) - Committee Member
etdurn: etd-08022010-173238
other_id: http://etd.library.pitt.edu/ETD/available/etd-08022010-173238/
other_id: etd-08022010-173238
citation:   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)  
document_url: http://d-scholarship-dev.library.pitt.edu/8836/1/Keyser_Sandra_ETD_corrected_082010.pdf