Two forms of (naphthalen-1-yl)boronic acid

Abstract

Two polymorphs of the title compound, C10H9BO2, were prepared by recystallization from different solvents at room temperature. Both forms demonstrate nearly identical molecular structures with all naphthalene group atoms located in one plane and all boronic acid atoms in another: the dihedral angles between these planes are 39.88 (5) and 40.15 (5)° for the two asymmetric molecules of the orthorhombic form and 40.60 (3)° for the single asymmetric molecule in the monoclinic form. In each extended structure, molecules form dimers, connected via two O—H...O hydrogen bonds. The dimers are connected by further O—H...O hydrogen bonds, forming layered networks in the (001) plane and the (100) plane in the orthorhombic and monoclinic forms, respectively. The resulting layers are practically identical in both forms. However, these layers are shifted along the [010] axis in the two forms, resulting in a slightly more effective packing for monoclinic structure (packing index = 0.692) compared to the orthorhombic form (0.688).

Keywords

• crystal structure
• arylboronic acid
• hydrogen-bond network
• polymorph