Quantifying the Inter- and Intramolecular Interactions in Crystalline Phthalic Acid

All inter- and intramolecular interactions in the crystals of phthalic acid have been quantified from the topology of the electron density distribution obtained from low temperature (20 K) X-ray diffraction data and from theoretical calculations. Using the Quantum Theory of Atoms in Molecules (QTAIM) approach, all covalent bonds have been characterized by the electronic properties at their (3, −1) bond critical points as well as all noncovalent bonds of the type O···H (both strong and weak), C···C, O···O, O···C, and H···H. Integrated atomic charges and the derived molecular dipole moment are reported. Differentiation of the two faces of the pyramidalized sp2 carbon atoms is investigated via the electrostatic potential projected onto the molecular surface.