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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
Journal of the Chemical Society, Perkin Transactions 2
  • Bruce A. Hathaway
  • Graeme M. Day
  • Michael A. Lewis
  • Rainer Glaser, Missouri University of Science and Technology
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.

Department(s)
Chemistry
Document Type
Article - Journal
Document Version
Citation
File Type
text
Language(s)
English
Rights
© 1998 Royal Society of Chemistry, All rights reserved.
Publication Date
12-1-1998
Publication Date
01 Dec 1998
Disciplines
Citation Information
Bruce A. Hathaway, Graeme M. Day, Michael A. Lewis and Rainer Glaser. "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 Iss. 12 (1998) p. 2713 - 2719 ISSN: 0300-9580
Available at: http://works.bepress.com/rainer-glaser/143/