Molecular and crystal structure of squaric acid (3,4-dihydroxy-3-cyclobutene-1,2-dione) at 121 /sup 0/C: A neutron diffraction study
The molecular and crystal structure of squaric acid (3,4-dihydroxy-3-cyclobutene-1,2-dione) has been determined by neutron diffraction techniques at 121/sup 0/C, a temperature above that of the monoclinic to tetragonal phase transition (approx.100/sup 0/C). The high-temperature structure is in space group I4/m, a=c=6.137(2) A, b=5.337(2) A. Least-squares refinement has been carried out with 25 variable parameters and 276 reflections, to yield an unweighted R value (on F/sup 2/) of 0.042. The squaric acid molecule has point symmetry 4/m, and the hydrogen atom is ''disordered'' about the inversion center at the midpoint of the OxxxO hydrogen bond. Hydrogen-bonding parameters are O--H 1.014(4), HxxxO 1.536(5) A, OxxxO 2.548(2) A, angle O--HxxxO 176.2(6) /sup 0/. The tetragonal structure corresponds closely to that obtained from the atomic parameters determined in the monoclinic phase at 25/sup 0/C, by averaging over the pseudofourfold symmetry.
- Research Organization:
- Chemistry Department, Brookhaven National Laboratory, Upton, New York 11973
- OSTI ID:
- 5311746
- Journal Information:
- J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 67:11; ISSN JCPSA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400301* -- Organic Chemistry-- Chemical & Physicochemical Properties-- (-1987)
CARBOXYLIC ACIDS
CHEMICAL BONDS
COHERENT SCATTERING
CRYSTAL STRUCTURE
DIFFRACTION
HYDROXY ACIDS
MOLECULAR STRUCTURE
NEUTRON DIFFRACTION
ORGANIC ACIDS
ORGANIC COMPOUNDS
SCATTERING