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Figure 2
Crystal structures of 2,4-di­nitro­cinnamic acid (top) and 3,5-di­nitro­cinnamic acid (bottom) and the role of the C—H⋯O=C weak hydrogen bonds. Why do the carboxyl groups hydrogen bond around different symmetry elements in these two structures?

IUCrJ
Volume 13| Part 5| September 2026|
ISSN: 2052-2525
https://doi.org/10.1107/S2052252526006676