Standard molar enthalpies of formation, vapour pressures, and enthalpies of sublimation of 2-chloro-4-nitroaniline and 2-chloro-5-nitroaniline

The standard (<f>po=0.1</f> MPa) molar enthalpies of formation for crystalline 2-chloro-4-nitroaniline and 2-chloro-5-nitroaniline were derived from the standard molar enthalpies of combustion, in oxygen, at the <f>T=298.15</f> K, measured by rotating bomb combustion calorimetry. The Knudsen mass-loss effusion technique was used to measure the vapour pressures of the crystals as function of temperature, and the standard molar enthalpies of sublimation, at <f>T=298.15</f> K, were derived by the Clausius–Clapeyron equation. Direct measurements of the standard molar enthalpies of sublimation, using Calvet microcalorimetry, for 2-chloro-4-nitroaniline and 2-chloro-5-nitroaniline confirmed the values derived from the Knudsen technique. <tbl loc="display"><tblbdy TOP-STUBS="0" LEFT-STUBS="0" BOTTOM-STUBS="0" RIGHT-STUBS="0"><r><c CSPAN="1" RSPAN="1" CA="L" RA="T"><top-border type="bar" style="s"></c><c CSPAN="1" RSPAN="1" CA="L" RA="T"><top-border type="bar" style="s"><bottom-border type="bar" style="s"><f>ΔfHm0</f> (cr)</c><c CSPAN="1" RSPAN="1" CA="L" RA="T"><top-border type="bar" style="s"><bottom-border type="bar" style="s"><f>ΔcrgHm0</f></c><c CSPAN="1" RSPAN="1" CA="L" RA="T"><top-border type="bar" style="s"><bottom-border type="bar" style="s"></c></r><r><c CSPAN="1" RSPAN="1" CA="L" RA="T"><bottom-border type="bar" style="s"></c><c CSPAN="1" RSPAN="1" CA="L" RA="T"><bottom-border type="bar" style="s">(kJ <f>·</f> mol−1)</c><c CSPAN="1" RSPAN="1" CA="L" RA="T"><bottom-border type="bar" style="s">(kJ <f>·</f> mol−1)</c><c CSPAN="1" RSPAN="1" CA="L" RA="T"><bottom-border type="bar" style="s"></c></r><r><c CSPAN="1" RSPAN="1" CA="L" RA="T"></c><c CSPAN="1" RSPAN="1" CA="L" RA="T"></c><c CSPAN="1" RSPAN="1" CA="L" RA="T">Calvet</c><c CSPAN="1" RSPAN="1" CA="L" RA="T">Knudsen</c></r><r><c CSPAN="1" RSPAN="1" CA="L" RA="T">2-Chloro-4-nitroaniline (2-Cl-4-NO2-C6H3NH2)</c><c CSPAN="1" RSPAN="1" CA="L" RA="T">−74.9 ± 1.4</c><c CSPAN="1" RSPAN="1" CA="L" RA="T">101.8 ± 1.8</c><c CSPAN="1" RSPAN="1" CA="L" RA="T">102.6 ± 1.5</c></r><r><c CSPAN="1" RSPAN="1" CA="L" RA="T"><bottom-border type="bar" style="s">2-Chloro-5-nitroaniline (2-Cl-5-NO2-C6H3NH2)</c><c CSPAN="1" RSPAN="1" CA="L" RA="T"><bottom-border type="bar" style="s">−71.0 ± 1.5</c><c CSPAN="1" RSPAN="1" CA="L" RA="T"><bottom-border type="bar" style="s">100.3 ± 2.2</c><c CSPAN="1" RSPAN="1" CA="L" RA="T"><bottom-border type="bar" style="s">101.0 ± 1.6</c></r></tblbdy></tbl> Additionally, standard enthalpies of formation were estimated by employing two different methodologies. One is based on the Cox scheme and the other one, much more accurate, is based on first-principles calculations. The theoretical calculations were performed at the AM1, B3LYP/6-31+G** and BP86/6-31+G** levels of theory. Estimated values are in good agreement with the reported experimental numbers. [Copyright &y& Elsevier]