Studies on nitrophenols. Part IV. The standard enthalpies of combustion and formation of 1,2-dihydroxybenzene, 1,2- and 1,4-nitrophenol

Abstract

Using a static oxygen-bomb calorimeter, the standard enthalpies of combustion at 298.15 K of 1,2-nitrophenol, the yellow dimorph of 1,4-nitrophenol and of 1,2-dihydroxybenzene were determined as −2873.27±0.62, −2863.21±0.54 and −2865.49±0.74 kJ mole−1, respectively. The corresponding standard enthalpies of formation were −202.4±1.0, −212.4 ±1.0 and −353.1±1.1 kJ mole−1. The enthalpy of transition of the white to yellow dimorph of 1,4-nitrophenol was determined as 0.07±0.08 kJ mole−1. The lower limit for the strengths of the intramolecular H-bonds in 1,2-nitrophenol and 1,2-dihydroxybenzene was estimated as ∼ 10 kJ mole−1.