ABSTRACT

Thermodynamic properties of 9,9-dimethylxanthene and 2,7-di-tert-butyl-9,9-dimethylxanthene for the condensed and gas states were derived from experimental and computational studies. Static-bomb combustion calorimetry, vacuum drop microcalorimetry and the Knudsen effusion techniques were used. Computational calculations of the enthalpies of hypothetical reactions in the gaseous phase, using the G3(MP2)//B3LYP composite method, were performed for the two xanthene derivatives. Natural bond orbital (NBO) calculations were also performed to ascertain the structure and reactivity of these compounds. The energetic effects caused by replacing hydrogen atoms in the xanthene moiety by methyl and tertbutyl groups yielding 9,9-dimethylxanthene and 2,7-di-tert-butyl-9,9-dimethylxanthene species were determined from direct comparison of their standard (po = 0.1 MPa) molar enthalpies of formation in the gaseous phase, at T = 298.15 K.

Compounds

#	Formula	Name
1	CO2	carbon dioxide
2	H2O	water
3	O2	oxygen
4	C15H14O	9,9-dimethylxanthene
5	C23H30O	2,7-di-tert-butyl-9,9-dimethylxanthene

Datasets

The table above is generated from the ThermoML associated json file (link above). POMD and RXND refer to PureOrMixture and Reaction Datasets. The compound numbers are included in properties, variables, and phases, if specificied; the numbers refer to the table of compounds on the left.
Type	Compound-#	Property	Variable	Phase	Method	#Points
POMD	4	Normal melting temperature, K ; Crystal		Crystal Liquid Air at 1 atmosphere	DTA	1
POMD	4	Molar enthalpy of vaporization or sublimation, kJ/mol ; Crystal	Temperature, K; Crystal	Crystal Gas	Static calorimetry	1
POMD	4	Molar enthalpy, kJ/mol ; Gas	Temperature, K; Gas	Gas Crystal	Drop calorimetry	1
POMD	5	Normal melting temperature, K ; Crystal		Crystal Liquid Air at 1 atmosphere	DTA	1
POMD	5	Molar enthalpy of vaporization or sublimation, kJ/mol ; Crystal	Temperature, K; Crystal	Crystal Gas	Static calorimetry	1
POMD	5	Vapor or sublimation pressure, kPa ; Crystal	Temperature, K; Crystal	Crystal Gas	Calculated from knudsen effusion weight loss	12
POMD	5	Molar enthalpy, kJ/mol ; Gas	Temperature, K; Gas	Gas Crystal	Drop calorimetry	1
RXND	4 1 2 3	Specific internal energy of reaction at constant volume, J/g			Static bomb calorimetry	1
RXND	5 1 2 3	Specific internal energy of reaction at constant volume, J/g			Static bomb calorimetry	1

Thermodynamics Research Center / ThermoML | Journal of Chemical Thermodynamics

Thermochemical studies on two alkyl-bulky substituted xanthene derivatives: 9,9-dimethylxanthene and 2,7-di-tert-butyl-9,9-dimethylxanthene

Freitas, V. L. S.[Vera L. S.], Gomes, J. R. B.[Jose R. B.], Ribeiro da Silva, M. D. M. C.[Maria D. M. C.]

ABSTRACT