The crystal structure of crotonohydroxamic acid, CH3CH=CHC(O)NHOH 5 contains centrosymmetrically-related pairs of acid molecules, with a short contact of 3.36 angstrom between the alpha-carbon atoms. The observed arrangement provides excellent alignment for a solid-state ene reaction, but, apparently, the threshold temperature for such a process cannot be realized. The hydrogen bonding patterns observed include C(5) chains and both R-2(4) (10) and R-4(4)(18) ring systems. Facile preparation of metal salts of the acid is reported, as well as discussion of the effect of heating and Co-60 gamma-irradiation of the materials.