Enthalpy of Formation of C₂H₂O₄ (Oxalic Acid) from High-Level Calculations and the Active Thermochemical Tables Approach

Journal Article · 22 March 2019 · Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory

DOI: https://doi.org/10.1021/acs.jpca.8b12329 · OSTI ID:1530415

Feller, David  ^[1]; Bross, David H.  ^[2]; Ruscic, Branko  ^[3]

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1. Washington State Univ., Pullman, WA (United States)
2. Argonne National Lab. (ANL), Argonne, IL (United States)
3. Argonne National Lab. (ANL), Argonne, IL (United States); The Univ. of Chicago, Chicago, IL (United States)

High-level coupled cluster calculations obtained with the Feller–Peterson–Dixon (FPD) approach and new data from the most recent version of the Active Thermochemical Tables (ATcT) are used to reassess the enthalpy of formation of gas-phase C₂H₂O₄ (oxalic acid). The theoretical value was further calibrated by comparing FPD and ATcT gas-phase enthalpies of formation for H₂CO (formaldehyde) and the two low-lying conformations of C₂H₄O₂ (syn and anti acetic acid). The FPD approach produces a theoretical enthalpy of formation of gas-phase oxalic acid of –732.2 ± 4.0 kJ/mol at 298.15 K (–721.8 ± 4.0 kJ/mol at 0 K). An independently obtained ATcT value, based on reassessing the existent experimental determinations and expanding the resulting thermochemical network with select mid-level composite theoretical results, disagrees with several earlier recommendations that were based solely on experimental determinations but is in excellent accord with the current FPD value. The inclusion of the latter in the most recent ATcT thermochemical network produces a further refined value for the gas-phase enthalpy of formation, –731.6 ± 1.2 kJ/mol at 298.15 K (–721.0 ± 1.2 kJ/mol at 0 K). In conclusion, the condensed-phase ATcT enthalpy of formation of oxalic acid is –829.7 ± 0.5 kJ/mol, and the resulting sublimation enthalpy is 98.1 ± 1.3 kJ/mol, both at 298.15 K.

• Research Organization: Argonne National Laboratory (ANL), Argonne, IL (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: AC02-06CH11357
• OSTI ID: 1530415
• Journal Information: Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory, Vol. 123, Issue 16; ISSN 1089-5639
• Publisher: American Chemical SocietyCopyright Statement
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
Active Thermochemical Tables
electronic structure theory
enthalpy of formation
high-level theory