Crystal structure, packing features, DFT evaluation of intermolecular hydrogen bonds, and crystal lattice energy of a polymorph of 4-oxo-4-phenylbutanoic acid

Abstract

Different crystal forms of pharmaceutically important compounds demonstrate non-equivalent physical properties and, thus, bioactivity. Taking into consideration the polymorphism is crucial for many applications due to the prominent variation in properties of solids of the same chemical substance but with different crystal packing. The structure of 4-oxo-4-phenylbutanoic acid, C₁₀H₁₀O₃, at 120 K has monoclinic (P2₁/c) symmetry and is a Z = 8, Z′ = 2 polymorph (γ-form). The previously published two polymorphs with CCDC codes VERMAG (α-form) and VERMAG01 (β-form) crystallize with Z = 4, Z′ = 1 in the monoclinic space groups P2₁/c [a = 15.071 (10), b = 5.435 (9), c = 16.058 (10), β = 129.57 (10)°] and P2₁/n [a = 12.728 (6), b = 5.200 (3), c = 14.426 (6), β = 111.33 (3)°], respectively. Reported herein polymorph has a significantly larger cell volume of 1754.51 ų [a = 15.2673 (6), b = 5.2028 (2), c = 22.3063 (8), β = 98.0217 (7)°]. Structurally, the γ-form differs from the two other known (RMSD does not exceed 0.2 Å). Only reported herein polymorph contains weak attractive C7—H7A···O3A close contacts between two neighboring molecules, giving some structural variety of the two crystallographically independent molecules as well as slight non-coplanarity between their phenyl rings. The previously reported polymorphs demonstrate carbonyl groups at position 4 unaffected. All polymorphs contain dimers of molecules bounded by two equivalent intermolecular hydrogen bonds. Investigation of three polymorphs of 4-oxo-4-phenylbutanoic acid highlights the importance of understanding the relationship between various parameters such as packing density, presence of different interactions within the crystal, and energy of the crystal lattice. This is of great importance for the development of new materials with specific physical properties and applications in various fields of science and technology, such as dyes and pigments, high-energy materials, and pharmaceuticals.