Thermodynamics Research Center / ThermoML | Thermochimica Acta

Melting temperature and heat of fusion of cytosine revealed from fast scanning calorimetry

Abdelaziz, A., Zaitsau, D.H., Mukhametzyanov, T.A., Solomonov, B.N., Cebe, P., Verevkin, S.P., Schick, C.
Thermochim. Acta 2017, 657, 47-55
ABSTRACT
Thermophysical properties in the melting range of cytosine, one of the five nucleobases of DNA and RNA, are hard to determine because of the low thermal stability of the compound and the high vapor pressure. As for other biomolecules fast heating rates allow melting of cytosine without detectable decomposition. By applying fast scanning calorimetry with the heating rate at 6000 K s.1 we succeeded to avoid decomposition and determine the melting temperature of cytosine (extrapolated to zero heating rate), as Tfus=(606 +- 4) K, the glass transition temperature of the supercooled liquid state as Tg =(388 +- 3) K, cold-crystallization temperature as Tcryst =(448 +- 8) K, and the liquid state molar heat capacity Cpdeg ,m(l) =(272 +- 2) J mol.1 K.1 at 423 K. Taking into account the temperature dependent mass loss of the nanogram sized sample (up to 25% during the melting scan) we obtained the molar enthalpy of fusion of cytosine as AcrH (T ) l fus = (35 +- 4) kJ mol.1 in good agreement with the adjusted molar enthalpy of crystallization Al H (T ) cr fus =(34 +- 2) kJ mol.1.
Compounds
# Formula Name
1 C4H5N3O 4-amino-2-hydroxypyrimidine
2 C14H10 anthracene
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
  • Normal melting temperature, K ; Crystal
  • Crystal
  • Liquid
  • Air at 1 atmosphere
  • DTA
  • 1
  • POMD
  • 1
  • Triple point temperature, K ; Glass
  • Glass
  • Liquid
  • Air at 1 atmosphere
  • DSC
  • 1
  • POMD
  • 1
  • Molar enthalpy of transition or fusion, kJ/mol ; Crystal
  • Crystal
  • Liquid
  • Air at 1 atmosphere
  • DSC
  • 1
  • POMD
  • 1
  • Molar heat capacity at constant pressure, J/K/mol ; Metastable liquid
  • Temperature, K; Metastable liquid
  • Pressure, kPa; Metastable liquid
  • Metastable liquid
  • Small sample (50 mg) DSC
  • 5
  • POMD
  • 2
  • Molar enthalpy of transition or fusion, kJ/mol ; Crystal
  • Crystal
  • Liquid
  • Air at 1 atmosphere
  • DSC
  • 1