Thermodynamics Research Center / ThermoML | Journal of Chemical and Engineering Data

Thermophysical Study of 2-Thiobarbituric Acids by Differential Scanning Calorimetry

Roux, M. V.[MarIa Victoria], Notario, R.[Rafael], Segura, M.[Marta], Chickos, J. S.[James S.]
J. Chem. Eng. Data 2012, 57, 2, 249-255
ABSTRACT
The present study reports a differential scanning calorimetry (DSC) study of 2-thiobarbituric acid [CAS Registry No. 504-17-6] and its derivative 1,3-diethyl-2-thiobarbituric acid [CAS Registry No. 5217-47-0] in the temperature interval from T = 268 K to their respective melting temperatures. Temperatures, enthalpies, and entropies of fusion of both compounds are reported. 2-Thiobarbituric acid exhibits solid solid phase transitions in the temperature interval studied. The polymorphic form of commercially available 2-thiobarbituric acid was identified by powder X-ray diffraction comparisons with the literature, and the heat capacity was measured from T = (268 to 430) K, temperatures below the first observable phase transition. The heat capacity of 1,3-diethyl-2-thiobarbituric acid was measured from T = (268 to 365) K. Commercially available 1,3-diethyl-2-thiobarbituric acid was likewise characterized by its X-ray powder diffraction pattern. Total phase change entropies and heat capacities of the two materials were also estimated by group additivity.
Compounds
# Formula Name
1 C4H4N2O2S 2-mercapto-4,6-pyrimidinediol
2 C8H12N2O2S 1,3-diethyl-2-thiobarbituric acid
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 Constraint Phase Method #Points
  • POMD
  • 1
  • Molar enthalpy of transition or fusion, kJ/mol ; Crystal 4
  • Crystal 4
  • Crystal 3
  • Air at 1 atmosphere
  • DSC
  • 1
  • POMD
  • 1
  • Molar enthalpy of transition or fusion, kJ/mol ; Crystal 3
  • Crystal 3
  • Crystal 2
  • Air at 1 atmosphere
  • DSC
  • 1
  • POMD
  • 1
  • Molar enthalpy of transition or fusion, kJ/mol ; Crystal 2
  • Crystal 2
  • Crystal 1
  • Air at 1 atmosphere
  • DSC
  • 1
  • POMD
  • 1
  • Molar enthalpy of transition or fusion, kJ/mol ; Crystal 1
  • Crystal 1
  • Liquid
  • Air at 1 atmosphere
  • DSC
  • 1
  • POMD
  • 1
  • Triple point temperature, K ; Crystal 4
  • Crystal 4
  • Crystal 3
  • Air at 1 atmosphere
  • DTA
  • 1
  • POMD
  • 1
  • Triple point temperature, K ; Crystal 3
  • Crystal 3
  • Crystal 2
  • Air at 1 atmosphere
  • DTA
  • 1
  • POMD
  • 1
  • Triple point temperature, K ; Crystal 2
  • Crystal 2
  • Crystal 1
  • Air at 1 atmosphere
  • DTA
  • 1
  • POMD
  • 1
  • Triple point temperature, K ; Crystal 1
  • Crystal 1
  • Liquid
  • Air at 1 atmosphere
  • DTA
  • 1
  • POMD
  • 1
  • Molar heat capacity at constant pressure, J/K/mol ; Crystal 4
  • Temperature, K; Crystal 4
  • Pressure, kPa; Crystal 4
  • Crystal 4
  • Small sample (50 mg) DSC
  • 36
  • POMD
  • 2
  • Molar enthalpy of transition or fusion, kJ/mol ; Crystal
  • Crystal
  • Liquid
  • Air at 1 atmosphere
  • DSC
  • 1
  • POMD
  • 2
  • Triple point temperature, K ; Crystal
  • Crystal
  • Liquid
  • Air at 1 atmosphere
  • DTA
  • 1
  • POMD
  • 2
  • Molar heat capacity at constant pressure, J/K/mol ; Crystal 4
  • Temperature, K; Crystal 4
  • Pressure, kPa; Crystal 4
  • Crystal 4
  • Small sample (50 mg) DSC
  • 23