Synthesis and Molecular Structures of the Lowest Melting Odd- and Even-Numbered [alpha],[beta]-Unsaturated Carboxylic Acids-(E)-Hept-2-Enoic Acid and (E)-Oct-2-Enoic Acid

The molecular structures of the two lowest melting odd- and even-numbered [alpha],[beta]-unsaturated carboxylic acids-(E)-hept-2-enoic acid (C7) and (E)-oct-2-enoic acid (C8)-are herein reported. The title compounds were crystallized by slow evaporation of ethanolic solutions at -30 °C. C7 crystallizes in the triclinic space group P 1 - with two molecules in the unit cell and C8 in the monoclinic space group C2/c with eight molecules in the unit cell. The unit cell parameters for C7 are: a = 5.3049(2) Å, b = 6.6322(3) Å, c = 11.1428(5) Å, [alpha] = 103.972(3)°, [beta] = 97.542(3)°, γ = 90.104(3)°, and V = 376.92(3) Å3 (T = 150(2) K). The unit cell parameters for C8 are: a = 19.032(10) Å, b = 9.368(5) Å, c = 11.520(6) Å, [beta] = 123.033(11)°, and V = 1721.80(16) Å3 (T = 200(2) K).