Molecular Aggregations in Crystals of Butene Isomers Determined at High Pressure

The crystal structures of all four ambient-condition gaseous butene isomers have been determined, for the first time, by high-pressure single-crystal X-ray diffraction. 1-Butene (but-1-ene, B), cis-2-butene ((2Z)-but-2-ene, CB), trans-2-butene ((2E)-but-2-ene, TB), and isobutene (2-methylprop-1-ene, IB) at high pressure and room temperature froze at 3.65, 1.55, 0.50, and 1.40 GPa, respectively. B, CB, TB, and IB crystallize in the centrosymmetric space groups of Pnma, C2/c, P21/c, and P63/m, respectively. All of these crystals remain stable within the investigated pressure range. The physical properties of the studied butene isomers have been correlated with their molecular structures, interatomic distances, and molecular packing.