Experimental and Computational Study of the Thermochemistry of the Fluoromethylaniline Isomers

Abstract

The standard (po = 0.1 MPa) molar enthalpies of formation in the condensed phase of seven isomers of fluoromethylaniline were derived from the standard molar energies of combustion, in oxygen, to yield CO2(g), N2(g) and HF.10H2O(l), at T = 298.15 K, measured by rotating bomb combustion calorimetry. The standard molar enthalpies of vaporization or sublimation of these compounds, also at T = 298.15 K, were determined using Calvet microcalorimetry, while the enthalpies of fusion of the solid compounds were determined by differential scanning calorimetry. The standard molar enthalpies of formation in the gaseous phase, at T = 298.15 K, were derived from the former two experimental quantities. G3MP2//B3LYP calculations were performed for all possible fluoromethylanilines allowing the estimation of data for the isomers that were not studied experimentally. The Cox scheme was applied with two different approaches for the estimation of the standard molar enthalpies of formation of all the isomers studied, and this led to the conclusion that the literature values for the enthalpies of formation of the meta and para isomers of methylaniline seem to be not reliable. Further G3MP2//B3LYPs calculations on the methylaniline isomers yielded new values for the standard molar enthalpies of formation of the isomers of methylaniline, which have been tested under the Cox scheme, resulting in better estimates.

Combined experimental and computational thermochemistry of isomers of chloronitroanilines

“…The adequacy of the present computational approach for the estimation of the enthalpies of formation of halogenated anilines was already duly tested in several recent works [6,7,10]. Further, it was found in another work that the geometries of two chloronitroanilines optimized with the B3LYP exchange-correlation functional were in very good agreement with the experimental ones [14].…”

“…The present work is part of our broad interest on the thermochemistry of halogenated anilines, for which we have studied fluoroanilines [6,7], chloroanilines [8][9][10][11], bromoanilines [12], and iodoanilines [13]. Recently, two isomers of chloronitroaniline, 2-chloro-4-nitroaniline and 2-chloro-5-nitroaniline, were the object of a detailed experimental and computational study [14].…”

Experimental and computational thermochemistry of 1-phenylpyrrole and 1-(4-methylphenyl)pyrrole

“…In this case, the calculated value using the atomization reaction (equation (5)) almost matches the experimental one, with a deviation of only 0.3 kJ Á mol À1 . It is important to highlight that the D f H m ðgÞ of p-methylaniline, used in the reactions described by equations (6) and (7), to calculate the gas-phase enthalpy of formation of 1-(4-methylphenyl)pyrrole is a computational value, previously estimated in our Research Group through the G3(MP2)//B3LYP approach [49], once it was found huge differences between experimental and calculated values when the data available in the literature were applied.…”

Experimental thermochemical study of 4,5-dichloro-2-nitroaniline

“…The present work is a contribution to the thermochemical investigation of halogenated anilines and nitroanilines carried out by the Molecular Energetics Research Group of the University of Porto, from which the fluoroanilines [3,4], chloroanilines [5][6][7][8], bromoanilines [9], iodoanilines [10], monochloronitroanilines [11,12], and two dichloro-4-nitroaniline isomers [13] have already been studied. This paper reports the standard ðp ¼ 0:1 MPaÞ molar enthalpy of formation, of 4,5-dichloro-2-nitroaniline, in the crystalline phase, at T = 298.15 K, derived from the standard massic energy of combustion, in oxygen, at the same temperature, measured by rotating-bomb combustion calorimetry.…”