Presentation Title

NICs Difference: Determination of Relative Aromaticity

Faculty Mentor

Kimberley Cousins

Start Date

17-11-2018 12:30 PM

End Date

17-11-2018 2:30 PM

Location

CREVELING 105

Session

POSTER 2

Type of Presentation

Poster

Subject Area

physical_mathematical_sciences

Abstract

Keywords:Aromatic, Aromaticity, Computational Chemistry, NMR,

Aromatic compounds commonly occur in pharmaceuticals, fuel additives, polymers and fragences. Key characteristics that make up an aromatic structure are the delocalization of pi electrons, particular stability of the structure, and the distinct electronic field generated, which can be detected running an NMR analysis. NICS (Nucleus Independent Chemical Shifts) is the computational method for predicting the NMR signals at specific points in space. In this Project, NICS differences between a given structure and a reference structure are investigated. NICS values are obtained using four programs: (1) Spartan to build the molecules, optimized structures (using the DFT B3LYP 6-311+G** method), and record geometry measurements such as bond lengths and angles; (2) Avogadro 1.2.0 to insert probe/ghost atoms for NICS, and to generate a GAMESS (General Atomic and Molecular Electronic Structure System) file; (3) a text editor to properly set up GAMESS input file; and (4) Submission to GAMESS via the GAMESSQ (Queue,GAMESS is the software GAMESSQ is the graphical interface) interface, to calculate shielding values for NICS. NICS scans method has taken criticism for not being able predict the relative aromaticity of rings of different sizes and charges. This method, uses the difference between NICS scan values at every 0.1 angstrom intervals from the origin 0.0 angstroms (center of the ring) up to 3 angstroms, for the structure in question and it’s corresponding reference structure. Results for known aromatics such as benzene and distorted benzenes, cycloheptatrienyl and cyclopentadienyl (anion, cation), and phenanthrene demonstrate the ability of NICS difference method to further enhance NICS scans in predicting relative aromaticity (NSF-HRD-1345163).

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Nov 17th, 12:30 PM Nov 17th, 2:30 PM

NICs Difference: Determination of Relative Aromaticity

CREVELING 105

Keywords:Aromatic, Aromaticity, Computational Chemistry, NMR,

Aromatic compounds commonly occur in pharmaceuticals, fuel additives, polymers and fragences. Key characteristics that make up an aromatic structure are the delocalization of pi electrons, particular stability of the structure, and the distinct electronic field generated, which can be detected running an NMR analysis. NICS (Nucleus Independent Chemical Shifts) is the computational method for predicting the NMR signals at specific points in space. In this Project, NICS differences between a given structure and a reference structure are investigated. NICS values are obtained using four programs: (1) Spartan to build the molecules, optimized structures (using the DFT B3LYP 6-311+G** method), and record geometry measurements such as bond lengths and angles; (2) Avogadro 1.2.0 to insert probe/ghost atoms for NICS, and to generate a GAMESS (General Atomic and Molecular Electronic Structure System) file; (3) a text editor to properly set up GAMESS input file; and (4) Submission to GAMESS via the GAMESSQ (Queue,GAMESS is the software GAMESSQ is the graphical interface) interface, to calculate shielding values for NICS. NICS scans method has taken criticism for not being able predict the relative aromaticity of rings of different sizes and charges. This method, uses the difference between NICS scan values at every 0.1 angstrom intervals from the origin 0.0 angstroms (center of the ring) up to 3 angstroms, for the structure in question and it’s corresponding reference structure. Results for known aromatics such as benzene and distorted benzenes, cycloheptatrienyl and cyclopentadienyl (anion, cation), and phenanthrene demonstrate the ability of NICS difference method to further enhance NICS scans in predicting relative aromaticity (NSF-HRD-1345163).