Synthesis and experimental and theoretical characterization of m-fluorosulfinylaniline

Abstract

The synthesis of m-fluorosulfinylaniline together with a tentative assignment of the vibrational, NMR and mass spectra, are reported. Quantum chemical calculations predict two stable conformers, with very similar energies, both of which possess in the liquid phase syn structure of the -N=S=O moiety (syn of the S=O double bond relative to the C-N single bond). Both conformers belong to C S symmetry group and differ by relative orientation of the fluorine atom and the NSO group. However, the FT-IR, FT-Raman and NMR spectra do not allow a distinction between these two conformers. The experimentally observed spectral data (FT-IR, FT-Raman, 1 H and 13 C and GC-Mass Spectrometry) of the title compound are compared with the spectral data obtained by quantum chemical calculations and gauge including atomic orbital (GIAO) method (DFT/B3LYP approximation using 6-311+G(df), 6-311++G(df,pd) and cc-pVTZ basis sets). Moreover, Natural Bond Orbital (NBO) analysis is applied for studying the stability of the molecule upon charge delocalization in order to provide an explanation of its electronic properties.

Assessment of the molecular structure and spectroscopic properties of CF3-substituted sulfinylaniline derivatives

“…Based on the Density Functional Theory (DFT), the Becke-style three parameter hybrid functional for the exchange part [19] with the Lee-Yang-Parr correlation function (B3LYP) [20] and the 6-311 + G(df) and 6-311 ++ G(df,pd) bases sets were applied for geometry optimization, conformational properties and vibrational frequency calculations of m -CF 3 ArNSO and o -CF 3 ArNSO conformational isomers. 1 H and 13 C NMR chemical shifts were calculated within a Gauge Invariant Atomic Orbital (GIAO) approach [21] which is one of the most common approaches for calculating nuclear magnetic shielding tensors. On the other hand, intramolecular orbital interactions were evaluated by the Natural Bond Orbital analysis NBO [22] while the nature of intramolecular hydrogen bonds was evaluated using the AIM approach by means of AIM20 0 0 software [23] .…”

“…Besides, the assignment was supported by theoretical calculations with the B3LYP/6-311 ++ G(df,pd) approximation. Additional calculations were performed with the same purpose using the same theoretical approach and a less extended basis set (6-311 + G(df)) for 13 C and 15 N isotopically substituted versions of the compounds. The present discussion focus on the vibrational signals observed in Figs.…”

“…As it was reported previously [2 , 34-37] N = S and S = O stretching modes are strongly coupled therefore, these vibrations may be better described as antisymmetric and symmetric stretching modes of the sulfinyl group. The series of compounds studied by our research group showed that for halogen monosubstituted sulfinylaniline derivatives (X = F [12][13][14] and Cl [15 , 16] ), the characteristic stretching modes of the NSO group change in a larger or smaller degree according to the position of the substituent in the aromatic ring. Not only frequency values modify according to the position of the substituent, but they also change in response to the electronic density in the aromatic ring itself.…”

“…Fluoro-substituted compounds were reported as relevant starting materials with great potential in the pharmaceutical industry [9][10][11] . Our recent studies regarding the conformational and vibrational properties of a series of fluorine [12][13][14] and chlorine [15 , 16] monosubstituted Nsulfinylanilines proved that the properties vary according to the position of the substituent in the aromatic ring and the prevalence of different electronic effects. These halogen atoms interact through mesomeric ( + M) and inductive (-I) effects with different extents.…”

“…The high electronegativity of fluorine atoms make the C-F bonds one of the strongest for organic compounds, conferring additional stability to the molecule as a whole [17] . The compounds were obtained through the reaction of the corresponding aniline derivatives and thionyl chloride and were characterized by using FT IR, Raman, 1 H and 13 C NMR spectroscopies and GC/MS spectrometry. The assignment of the experimental spectra was achieved considering quantum chemical calculations derived from Density Functional Theory and data reported in literature for related compounds.…”