National Institute of Standards and Technology
Computational Chemistry Comparison and Benchmark DataBase
Release 18October 2016
NIST Standard Reference Database 101
IIExperimental data
IIICalculated data
IVData comparisons
VCost comparisons
VIInput and output files
VIITutorials and Units
VIIILinks to other sites
XOlder CCCBDB versions
XIII Vibrations
XIVReaction data
XVEntropy data
XVIBibliographic data
XVIIIon data
XVIIIBad calculations
XIXIndex of properties
XXH-bond dimers

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IV.A.4. (XIV.F.)

Relative enthalpies of isomers - Comparison of 298.15K enthalpies (kJ mol-1)

Isomers of C5H4O2

index Species CAS number Name Relative experimental enthalpy (kJ mol-1) sketch
a C5H4O2 930609 4-Cyclopentene-1,3-dione   sketch of 4-Cyclopentene-1,3-dione
b C5H4O2 980101 furfural 0.0 sketch of furfural
The calculated enthalpies include the calculated and scaled vibrational zero-point energy.
Methods with predefined basis sets
semi-empirical AM1 -275.7 a
0.0 b
PM3 -260.5 a
0.0 b
PM6 -66.1 a
0.0 b
composite G1 -267.7 a
0.0 b
G2MP2 -266.1 a
0.0 b
G2 -267.3 a
0.0 b
G3 -267.4 a
0.0 b
G3B3 -250.8 a
0.0 b
G3MP2 -266.6 a
0.0 b
G4 -248.2 a
0.0 b
CBS-Q -263.4 a
0.0 b

Methods with standard basis sets
NC = not calculated
For descriptions of the methods (AM1, HF, MP2, ...) and basis sets (3-21G, 3-21G*, 6-31G, ...) see the glossary in section I.C. Predefined means the basis set used is determined by the method.
gaw refers to the group additivity method implemeted in the NIST Chemistry Webbook.

See section III.C.1 List or set vibrational scaling factors to change the scale factors used here.
See section III.C.2 Calculate a vibrational scaling factor for a given set of molecules to determine the least squares best scaling factor.