Computational Chemistry Comparison and Benchmark DataBase Release 22 (May 2022) Standard Reference Database 101 National Institute of Standards and Technology
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Geometry for C₅H₄O₂ (4-Cyclopentene-1,3-dione) ¹A₁ C2V

B3LYP/3-21G

For information on specific bond angles or dihedrals see the geometry comparison page in section Comparisons > Geometry > Bonds, angles.