Experimental and computational study on the molecular energetics of the three monofluoroanisole isomers

Experimental and Computational Thermochemical Study of the Three Monofluorophenol Isomers

“…Zero-point vibrational energies and fundamental vibrational frequencies were scaled by a factor of 0.9887 and 0.9688, respectively . The above-mentioned exchange-correlation functional was chosen since a previous work devoted to the thermochemistry of fluoroanisoles yielded an estimation of accurate gas-phase enthalpies of formation for this class of compounds. Also, it has been demonstrated that this theoretical level yields to a practically perfect agreement between the theoretical and experimental infrared spectra of phenol …”

“…In Table 5 are also presented the literature values for the enthalpies of formation in the gas phase for benzene, fluorobenzene, phenol, anisole, aniline, monofluoroanisoles, 88 and monofluoroanilines 60 and the respective enthalpic increment for introducing a fluorine atom in the different position of the aromatic ring, δ -F , of benzene, phenol, anisole, and aniline. From the results presented in Table 5 and from Figure 4, it is possible to observe a similar order of enthalpic increment for the substitution of a fluorine atom in ortho, meta, and para positions of the aromatic ring of phenol, anisole, and aniline: meta < para < ortho, with the exception of the 2-fluorophenol isomer, which has an enthalpic stability similar to the 3-fluorophenol isomer, due to an additional effect of stabilization caused by the existence of an intramolecular hydrogen bond between the fluorine atom and the hydrogen of the hydroxyl group, not present in the 2-fluoroanisole 88 or 2-fluoroaniline. 60 The fluorine atom exerts a σ electron-withdrawing inductive effect and a π electron-donating mesomeric effect on the aromatic ring.…”