Ganis, Paolo published the artcileThe crystal structure of a new form of the cyclic condensation product of methyl succinate (dimethyl 2,5-dihydroxy-l,4-cyclohexadiene-1,4-dicarboxylate: crystal form II, Computed Properties of 594-81-0, the publication is Atti Accad. Naz. Lincei Rend. Classe Sci. Fis. Mat. Nat. (1963), 35(1-2), 68-79, database is CAplus.
A 2nd crystal form of the title compound was crystallized from AcOEt as thick irregular prisms. Weissenberg photographs taken along the 3 principal axes with Cu Kα radiation established the triclinic space group P1̅ and the cell constants a 8.45 ± 0.05, b 6.90 ± 0.05, c 4.97 ±: 0.03 A., α 118° ± 1°, β 94° ± 1°, γ 94° ± 1°; d. (calculated) is 1.52. Positional parameters for C and O atoms were obtained from Patterson maps and refined by Fourier methods to R factors of 12.5 and 16.1% for [001] and [010] projections, by using B factors of 2.5 A.2. H atoms, placed in their stereochem. accepted positions, were included in structure-factor calculations but not refined. A list of 216 F0 and F0 is given. Bond distances and angles are within the accepted values reported for analogous structures. Contact distances exclude the possibility of intermol. H-bond formation. A very nearly planar mol. results, however, from intramol. H bonding between the OH and COOH groups adjacent on the planar cyclohexadiene nucleus. The C:C distance of 1.33 ± 0.04 A. is compatibile only with an enolic form of the compound
Atti Accad. Naz. Lincei Rend. Classe Sci. Fis. Mat. Nat. published new progress about 594-81-0. 594-81-0 belongs to bromides-buliding-blocks, auxiliary class Bromide,Aliphatic hydrocarbon chain, name is 2,3-Dibromo-2,3-dimethylbutane, and the molecular formula is C6H12Br2, Computed Properties of 594-81-0.
Referemce:
https://en.wikipedia.org/wiki/Bromide,
bromide – Wiktionary