Experimental and Computational Study on the Thermochemistry of Bromoanilines

Abstract

The standard (p ¼ 0:1 MPa) molar enthalpies of formation of 2-, 3-, and 4-bromoaniline, 2,4-, 2,5-, and 2,6-dibromoaniline, and 2,4,6-tribromoaniline were derived from the standard molar enthalpies of combustion, in oxygen, which yields CO 2 (g), N 2 (g), and HBr Á 600H 2 O(l), at T ¼ 298:15 K, measured by using rotating-bomb calorimetry.The standard molar enthalpies of sublimation, or vaporization, of these compounds at T ¼ 298:15 K were measured by using Calvet microcalorimetry, and so their standard molar enthalpies of formation in the gaseous state were derived. The enthalpies of fusion of the solid compounds were determined by DSC. The gas-phase enthalpies of formation were also estimated by density functional theory calculations performed at the BP86/6-31+G Ã level. As a result it is confirmed that thermodynamic data is consistent with intramolecular N-HÁÁÁBr hydrogen bonding.Aromatic amines are of great importance in biological and material sciences as well as in pharmaceutical and chemical industries. Halogenated anilines have gained the most focus of all of the aromatic amines, due to their high toxicity and wide uses. For example, they may be used as reagents or precursors for synthesizing organic dyes, in pigments, in agricultural agents, in pharmaceuticals and in the rubber industries.1,2 Haloanilines are frequently found in both effluents of waste water treatment plants and surface water, due to chemical degradation or biotransformation of pesticides and herbicides, or due to accidental spills and illegal release of industrial and municipal wastewater. 3 These compounds have been determined to induce several kinds of toxicity, like methemoglobinemia, splenotoxicity, hepatotoxicity, and nephrotoxicity. 2,4Because of their stability in the presence of air and humidity, and potentially attractive economics, 5,6 aniline and haloanilines have been also used in the synthesis of conducting polymers with applications in rechargeable batteries, electromagnetic interference shielding, electrochromic display devices, sensors, and electrocatalysis.The current work presents the results of calorimetric and computational thermochemistry studies on bromoanilines. The experimental investigation includes the determination of the standard massic energies of combustion in oxygen at T ¼ 298:15 K of the different bromoanilines using a rotatingbomb combustion calorimeter, from which the values of the standard molar enthalpies of formation in the condensed phase were derived. The determination of the standard molar enthalpies of sublimation or vaporization at T ¼ 298:15 K was done by using Calvet microcalorimetry with the high-temperature vacuum sublimation technique; these values allowed the derivation of the standard molar enthalpies of formation, in the gaseous state, of 2-, 3-, and 4-bromoaniline, 2,4-, 2,5-, and 2,6-dibromoaniline, and 2,4,6-tribromoaniline, which were compared with values estimated by the Cox scheme 7 and those obtained by density functional theory calculations. Experimental Materials.The three mono...

Experimental thermochemical study of 2,5- and 2,6-dichloro-4-nitroanilines

“…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, following the studies of fluoroanilines [6,7], chloroanilines [8][9][10][11], bromoanilines [12], iodoanilines [13] and monochloronitroanilines [14,15]. This paper reports the standard (p°= 0.1 MPa) molar enthalpies of formation, of 2,5-and 2,6-dichloro-4-nitroanilines, in the crystalline phase, at T = 298.15 K, derived from the standard massic energies of combustion, of those two compounds, in oxygen, at the same temperature, measured by rotating-bomb combustion calorimetry.…”

Gas phase enthalpies of formation of monobromophenols

“…As part of our interest on the thermochemistry of halogenated benzene derivatives and with a view of a better understanding of the energetic effect of the substitution of a bromine atom in the aromatic ring, we have studied, in previous works, the thermochemical properties of bromine substituted benzoic acids [1], naphthalenes [2], anilines [3], pyridines [4], indolines [5], and anisoles [6]. Hence, in this work, we carried out a detailed thermochemical study on the energetics of mono-bromo substituted phenol.…”

Combined experimental and computational thermochemistry of isomers of chloronitroanilines

“…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].…”