Thermochemical study of four isomers of dichloroanisole

Abstract

The present work reports the values of the gaseous standard ( p ∘ = 0.1 MPa) molar enthalpies of formation of four isomers of dichloroanisole: 2,3-, 2,4-, 2,6-, and 3,5-dichloroanisole, at T = 298.15 K. For all compounds, those values were derived from measurements of the standard molar energies of combustion in the condensed phase, using a rotating bomb combustion calorimeter, together with measurements of the standard molar enthalpies of sublimation or vaporization, measured by high temperature Calvet microcalorimetry. Moreover, the enthalpies and the temperatures of fusion for the crystalline isomers of dichloroanisoles were measured by differential scanning calorimetry. - Δ c U m ∘ ( cr, l ) / ( kJ · mol - 1 ) - Δ f H m ∘ ( cr, l ) / ( kJ · mol - 1 ) Δ cr, l g H m ∘ / ( kJ · mol - 1 ) 2,3-Dichloroanisole (cr) 3456.8 ± 1.5 201.3 ± 1.8 83.6 ± 1.5 2,4-Dichloroanisole (l) 3473.7 ± 1.4 184.4 ± 1.7 62.8 ± 0.7 2,6-Dichloroanisole (l) 3492.7 ± 1.5 165.4 ± 1.8 56.1 ± 0.7 3,5-Dichloroanisole (cr) 3453.2 ± 1.5 204.9 ± 1.8 79.0 ± 1.5 The derived standard molar enthalpies of formation in the gaseous phase, at T = 298.15 K, for the title compounds were compared with the same parameters estimated by the Cox scheme and interpreted in terms of molecular structure.