Stereoeletronic properties in organofluorine compounds

Author(s)

Vinícius Capriles Port

• Document type: Master's Dissertation
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Química
• Defense date: 2021-09-20

Examining board members

Rodrigo Antonio Cormanich; Matheus Puggina de Freitas; Cláudio Francisco Tormena

• Advisor: Rodrigo Antonio Cormanich

Abstract

In this dissertation, the effect of stereoelectronic properties of organofluorine compounds in different chemical phenomena were investigated. This was performed by studying different phe- nomena as conformational preferences and the spin-spin coupling constant (SSCC) transmission in organofluorine compounds. In the second chapter, stereoeletronic effects that govern the gauche preference in 1,2-difluoroethane were explored. This was performed by observing the preferred geometry adopted by DFE and some analogues, such as its respective chloride and bromide molecular systems, as well as sulfides, peroxides and ammonium boranes. Both DFE and its analogues were subjected to a scan upon the dihedral angle, from which nineteen geometries were obtained to form the potential energy curve (PEC). Upon these structures NBO methods were applied to obtain the hyperconjugative, electrostatic and sterics contributions that define the main PEC profile. It was observed that hyperconjugation is the driving force both in DFE and its analogues. Sterics was found to play a minor role, but was important in the change of conformer stability of DFE and the chlorine and bromine analogues. Electrostatics did not play an important role in stabilizing the main conformers, where it showed a clear preference for the anticlinal geometry in most systems. In the third chapter, the compound 2-(trifluoromethyl)thiophenol (TFT) was studied in regards to both its (SSCC), and the intramolecular non covalent interactions that govern the geometry of both of its main conformers: cis-TFT and trans-TFT. In the cis-TFT it was found that a bifurcated CF· · ·HS interaction was the responsible for the higher stability of this conformer in the gas phase. On the other hand the trans-TFT had an unusual CF· · ·SH interaction which was responsible for the prefered geometry of this conformer. It was also observed that the medium po- larity has an important role in the conformer populations, where the increase in polarity increases the trans-TFT conformer population. The interactions found were crucial for the stabilized ge- ometries of the compound but surprisingly werent the main transmission pathway for the J HF SSCC, where the main pathway relies on steric interactions in the trans-TFT conformer (AU)

• FAPESP's process: 19/21136-4 - Mechanistic studies for the evaluation of the Thorpe-Ingold effect of CF2 groups in intramolecular cyclization reactions
• Grantee: Vinícius Capriles Port
• Support Opportunities: Scholarships in Brazil - Master