Revisiting dibenzothiophene thermochemical data: Experimental and computational studies

Molecular energetics of 4-methyldibenzothiophene: An experimental study

“…The experimental thermochemical results reported in this study allowed us to derive the value of the standard molar enthalpy of formation of 4-methyldibenzothiophene, in the gaseous phase, D f H m ðgÞ ¼ ð161:2 AE 4:9Þ kJ Á mol À1 , which reflects an increment of À(50.1 ± 6.6) kJ Á mol À1 for the methylation of dibenzothiophene [15] in position 4. The sparse amount of experimental thermochemical data for other related methylated polycyclic sulfur compounds, does not allow a deep analysis of the result obtained.…”

“…The fundamental interest of contributing to an understanding of the structural effects on thermodynamic stabilities that are reflected in the gas-phase enthalpies of formation of the sulfur compounds motivated us to study S-containing aromatic and polyaromatic compounds [15][16][17].…”

“…are being developed from key experimental values or, in a complementary perspective, used as an independent confirmation of the accuracy of the experimental measurements. In a very recent paper [15], we have reported a critical review of the literature data for the dibenzothiophene (a moiety that is present in many other compounds turning it into a key species) which included new experimental and computational studies allowing the proposal of a key value for the enthalpy of formation for gaseous dibenzothiophene. Concerning the methyldibenzothiophene isomers, there is not any experimental enthalpy of formation in the gaseous phase, most probably due to the great difficulty of obtaining enough amounts of those compounds, in the high purity grade required for the thermochemical measurements.…”

“…c Computational result taken from reference[38]. d Experimental result taken from reference[15]. e Present work.…”

“…molar heat capacity values, between (150 and 550) K, are given in table S1 of the Supporting Information). ðgÞ=ðJ Á K À1 Á mol À1 Þ ¼ À9:00896 Á 10 À7 ðT=KÞ 3 þ 6:08937Á 10 À4 ðT=KÞ 2 þ 5:14695 Á 10 À1 ðT=KÞþ 16:8322 ðR 2 ¼ 0:9999Þ:ð4ÞThe uncertainty associated with the standard molar enthalpy of sublimation, at T = 298.15 K, D g cr H m ð298:15 KÞ, is twice the standard deviation of the mean and include the estimated uncertainties associated with the calibration procedure and the molar heat capacity for 4-methyldibenzothiophene in the gaseous state.The standard (p ¼ 0:1 MPa) molar enthalpy of formation of 4-methyldibenzothiophene in the gaseous state, at T = 298 15. K, D f H m ðgÞ ¼ ð161:2 AE 4:9Þ kJ Á mol À1 , was obtained by addition of the derived standard molar enthalpy of formation in the crystalline state, D f H m ðcrÞ ¼ ð70:9 AE 4:8Þ kJ Á mol À1 , and the standard molar enthalpy of sublimation D g cr H m ¼ ð90:3 AE 0:7Þ kJ Á mol À1 .…”