Experimental and computational energetic study of 1-R-2-phenylindole (R = H, CH3, C2H5)

Abstract

The standard (po=0.1MPa) molar energies of combustion, ΔcUmo, of 2-phenylindole, 1-methyl-2-phenylindole and 1-ethyl-2-phenylindole, in the crystalline state, were determined, at T=298.15K, using a static bomb combustion calorimeter. The vapour pressures as a function of the temperature for these compounds were measured by the Knudsen effusion technique and the standard molar enthalpies of sublimation were derived. From the experimental results, the standard (po=0.1MPa) molar enthalpies of formation in the condensed and gaseous phases, at T=298.15K, of 2-phenylindole, 1-methyl-2-phenylindole and 1-ethyl-2-phenylindole were calculated.Additionally, the gas-phase enthalpies of formation of these compounds and also for 1-ethylindole were estimated by G3(MP2) calculations. Enthalpies of formation, obtained using appropriate working reactions, were calculated and compared with the experimental data. The results were also analysed in terms of structural enthalpic group contributions.