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Updated: Jun 15, 2026

Evaluation of Oxidative Stress in Biological Samples Using the Thiobarbituric Acid Reactive Substances Assay
Published on: May 12, 2020
Experimental and computational thermochemical study and solid-phase structure of 5,5-dimethylbarbituric acid
María Victoria Roux1, Rafael Notario, Concepción Foces-Foces
1Instituto de Química Física Rocasolano, CSIC, Serrano 119, 28006 Madrid, Spain. victoriaroux@iqfr.csic.es
This study determined the thermochemical properties and solid-state structure of 5,5-dimethylbarbituric acid. Experimental and computational methods yielded precise enthalpy of formation and sublimation values, revealing its crystal structure stabilized by hydrogen bonds.
Area of Science:
- Thermochemistry
- Solid-state chemistry
- Computational chemistry
Background:
- 5,5-Dimethylbarbituric acid is a compound with potential applications.
- Understanding its thermochemical properties and solid-state structure is crucial for its utilization.
- Previous studies may lack comprehensive experimental and computational data.
Purpose of the Study:
- To experimentally and computationally determine the thermochemical properties of 5,5-dimethylbarbituric acid.
- To elucidate the solid-phase structure of the compound.
- To investigate the molecular and electronic structure in both solid and gas phases.
Main Methods:
- Static bomb combustion calorimetry for energy of combustion measurement.
- Transference (transpiration) method for enthalpy of sublimation determination.
- G3 level theoretical calculations and DFT for molecular structure and gas-phase properties.
- Single crystal X-ray diffraction for solid-state structure analysis.
Main Results:
- Standard molar enthalpy of formation in the crystalline state: -(706.4 ± 2.2) kJ·mol⁻¹.
- Enthalpy of sublimation at 298.15 K: (115.8 ± 0.5) kJ·mol⁻¹.
- Gas-phase enthalpy of formation at 298.15 K: -(590.6 ± 2.3) kJ·mol⁻¹.
- Crystal structure characterized by N-H···O=C and C-H···O=C hydrogen bonds forming a 3D network.
Conclusions:
- Experimental and computational results for enthalpy of formation show good agreement.
- The study provides a comprehensive thermochemical and structural dataset for 5,5-dimethylbarbituric acid.
- The molecular and supramolecular structures were investigated in both solid and gas phases.
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