Computed NMR shielding values of unsaturated five-membered-heterocyclic ring compounds and their benzo-analogs as a measure of aromaticity
- UNCW Author/Contributor (non-UNCW co-authors, if there are any, appear on document)
- Eddie Pittman (Creator)
- Institution
- The University of North Carolina Wilmington (UNCW )
- Web Site: http://library.uncw.edu/
- Advisor
- Ned Martin
Abstract: The gauge independent atomic orbital (GIAO) Hartree-Fock (HF) technique
with a 6-31 G(d, p) basis set was used to calculate the isotropic NMR shielding values of
a diatomic hydrogen probe above a set of unsaturated 5-membered heterocyclic aromatic
compounds and their benzo- analogs. It has been shown that this technique produced
results indicating substantial shielding of the probe over the center of aromatic rings. The
current study was conducted to determine if the computed shielding of a diatomic H2
probe is related quantitatively to the extent of aromaticity. Aromaticity is a chemical
property in which a conjugated ring of unsaturated bonds, lone pairs of electrons or
empty orbitals exhibits a stabilization due to conjugation alone. Aromaticity is both a
qualitative and quantitative concept. The qualitative aspect, which is the method for
identifying a molecule or species as either aromatic, non-aromatic or anti-aromatic, is
soundly understood, but the quantitative aspect of aromaticity is less well defined. There
are several established methods for measuring aromaticity quantitatively but they are
only loosely correlated. This study’s method (?s) for calculations done over the fivemembered
rings correlated well with Cyransky’s published data of ASE, ?, NICS(0),
NICS(1) and HOMA calculations to yield correlation coefficients of 0.64, 0.49, 0.66,
0.88 and 0.69, respectively. This study’s method (?s) with calculations done over the
heterocyclic ring portion of the benzo-analogs yielded a correlation coefficient of 0.67
when matched with Bird’s published ASE data.
Computed NMR shielding values of unsaturated five-membered-heterocyclic ring compounds and their benzo-analogs as a measure of aromaticity
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Created on 1/1/2008
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Additional Information
- Publication
- Thesis
- A Thesis Submitted to the University of North Carolina Wilmington in Partial Fulfillment Of the Requirements for the Degree of Master of Science
- Language: English
- Date: 2008
- Keywords
- Nuclear magnetic resonance, Aromaticity (Chemistry), Aromatic compounds, Aromatic compounds -- Magnetic properties
- Subjects
- Nuclear magnetic resonance
- Aromaticity (Chemistry)
- Aromatic compounds
- Aromatic compounds -- Magnetic properties