Centrosymmetric Structures of Three Substituted Malonic Acids

Crystal structures of 2-methylmalonic acid, 2-ethylmalonic acid and 2-phenylmalonic acid, which are derivatives of malonic acid and have found usefulness in diagnostics and biochemical evaluations as markers and organic synthesis, are reported. 2-Methylmalonic acid and 2-ethylmalonic acid both crystallize in triclinic P-1 space group with cell parameters of a = 5.1033(7), b = 5.4231(7), c = 10.0887(14) Å, α = 88.074(4), β = 89.999(5) and γ = 67.955(4)° for 2-methylmalonic acid, and a = 5.2073(4), b = 7.2258(6), c = 8.5655(6) Å, α = 88.086(2), β = 75.307(2) and γ = 85.904(3)° for 2-ethylmalonic acid, 2-phenylmalonic acid on the other hand crystallizes in monoclinic P 2 1 / c with cell parameters a = 8.6494(4), b = 5.48733(19), c = 17.1706(6) Å and β = 90.1068(17)°. The observed topology of the hydrogen bonding network is to a large extent dictated by the symmetrical substitution pattern with an open arrangement of hydrogen bonds. Each of the C=O double bonds in both 2-methylmalonic acid and 2-ethylmalonic acid is translationally offset, forming planar centrosymmetric carboxy-dimers. Molecules related by centre of inversion in spite of the constraints imposed by substituents are linked by O–H···O hydrogen bonds. This results in the formation of parallel zig-zag chains running along the [101] direction. In 2-phenylmalonic acid, the zig-zag molecular residue is parallely stacked with successive catemers. These laterally displaced catemers are also coiled in a twofold twist on the screw axis ( x , ½ + y , ½ − z ) along the b-glide ( x , ½ − y , ½ + z ) when viewed along the (101) plane. Graphical Abstract Crystal structures of 2-methylmalonic acid (I), 2-ethylmalonic acid (II) and 2-phenylmalonic acid (III), which are derivatives of malonic acid and have found usefulness in diagnostics and biochemical evaluations as markers and organic synthesis, are reported showing topology of hydrogen bonding network dictated by symmetric substitution pattern with an open arrangement of hydrogen bonds.