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Synthesis, structure, electrostatic properties and spectroscopy of 3-methyl-4,5,6,7-tetrafluoro-1H-indazole. An experimental and ab initio computational study

Synthesis, structure, electrostatic properties and spectroscopy of 3-methyl-4,5,6,7-tetrafluoro-1H-indazole. An experimental and ab initio computational study
Synthesis, structure, electrostatic properties and spectroscopy of 3-methyl-4,5,6,7-tetrafluoro-1H-indazole. An experimental and ab initio computational study
The azine of pentafluorobenzaldehyde had been previously prepared from pentafluorobenzaldehyde and hydrazine. However, the analogous reaction of 2,3,4,5,6-pentafluoroacetophenone 1 with hydrazine did not result in the formation of azine 3 but resulted instead in the formation of 3-methyl-4,5,6,7-tetrafluoro-1H-indazole, 4, via the hydrazone 2. The resulting indazole was characterized by high resolution mass spectroscopy and 1H-, 13C-, and 19F-NMR spectroscopy. The geometry and electrostatic properties of the parent indazole and its derivative, 4, were studied with ab initio quantum theory and density functional methods. Our optimized structure of the parent indazole computed at the MP2(fc)/6-311G** level is presumably more accurate than the structure derived from microwave measurements. The preferred conformer of 4 was determined from RHF/6-31G* energies and full normal mode analyses were used to characterize both conformers. The minimum structure of 4 was refined at the MP2(fc)/6-311G** level of theory and compared to the unsubstituted structure. The electrostatic properties of the parent indazole and 4 are discussed and compared to those of benzene and hexafluorobenzene calculated at the same level. Natural bond order (NBO) calculations were performed to rationalize the difference in direction of the dipole moments of the parent indazole and 4. The gauge-invariant atomic orbital (GIAO) method was employed to calculate atomic shielding tensors of the indazoles using density functional theory at the B3LYP/6-311+G(2d,p) level. The calculated chemical shifts were used to aid in assigning peaks in the NMR spectra
1364-5471
2713-2720
Hathaway, Bruce A.
88982730-bd18-46ed-bac2-1eafbe7ce69f
Day, Graeme
e3be79ba-ad12-4461-b735-74d5c4355636
Lewis, Michael
f046ffc3-6d03-4a51-9c3d-fa8fa6a01473
Glaser, Rainer
c209af9f-73ef-471a-a058-eb75fdad418e
Hathaway, Bruce A.
88982730-bd18-46ed-bac2-1eafbe7ce69f
Day, Graeme
e3be79ba-ad12-4461-b735-74d5c4355636
Lewis, Michael
f046ffc3-6d03-4a51-9c3d-fa8fa6a01473
Glaser, Rainer
c209af9f-73ef-471a-a058-eb75fdad418e

Hathaway, Bruce A., Day, Graeme, Lewis, Michael and Glaser, Rainer (1998) Synthesis, structure, electrostatic properties and spectroscopy of 3-methyl-4,5,6,7-tetrafluoro-1H-indazole. An experimental and ab initio computational study. Journal of the Chemical Society, Perkin Transactions 2, (12), 2713-2720. (doi:10.1039/A805580G).

Record type: Article

Abstract

The azine of pentafluorobenzaldehyde had been previously prepared from pentafluorobenzaldehyde and hydrazine. However, the analogous reaction of 2,3,4,5,6-pentafluoroacetophenone 1 with hydrazine did not result in the formation of azine 3 but resulted instead in the formation of 3-methyl-4,5,6,7-tetrafluoro-1H-indazole, 4, via the hydrazone 2. The resulting indazole was characterized by high resolution mass spectroscopy and 1H-, 13C-, and 19F-NMR spectroscopy. The geometry and electrostatic properties of the parent indazole and its derivative, 4, were studied with ab initio quantum theory and density functional methods. Our optimized structure of the parent indazole computed at the MP2(fc)/6-311G** level is presumably more accurate than the structure derived from microwave measurements. The preferred conformer of 4 was determined from RHF/6-31G* energies and full normal mode analyses were used to characterize both conformers. The minimum structure of 4 was refined at the MP2(fc)/6-311G** level of theory and compared to the unsubstituted structure. The electrostatic properties of the parent indazole and 4 are discussed and compared to those of benzene and hexafluorobenzene calculated at the same level. Natural bond order (NBO) calculations were performed to rationalize the difference in direction of the dipole moments of the parent indazole and 4. The gauge-invariant atomic orbital (GIAO) method was employed to calculate atomic shielding tensors of the indazoles using density functional theory at the B3LYP/6-311+G(2d,p) level. The calculated chemical shifts were used to aid in assigning peaks in the NMR spectra

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Published date: 1998
Organisations: Chemistry

Identifiers

Local EPrints ID: 343469
URI: http://eprints.soton.ac.uk/id/eprint/343469
ISSN: 1364-5471
PURE UUID: baa61837-51f5-435f-bab6-83b5a635445b
ORCID for Graeme Day: ORCID iD orcid.org/0000-0001-8396-2771

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Date deposited: 19 Oct 2012 13:57
Last modified: 17 Dec 2019 01:38

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