Molecular and crystal structure, lattice energy and DFT calculations of two 2′-(nitrobenzoyloxy)acetophenone isomers

The two isomers 2'-(4-nitrobenzoyloxy)acetophenone (systematic name: 2-acetylphenyl 4-nitrobenzoate) (I) and 2'-(2-nitrobenzoyloxy)acetophenone (systematic name: 2-acetylphenyl 2-nitrobenzoate) (II), both C15H11NO5, with para and ortho positions of the nitro substituent have been crystallized and studied. It is evident that the variation in the position of the nitro group causes a significant difference in the molecular conformations: the dihedral angle between the aromatic fragments in the molecule of I is 84.80 (4)degrees, while that in the molecule of II is 6.12 (7)degrees. Diffraction analysis revealed the presence of a small amount of water in the crystal of I. DFT calculations of the molecular energy demonstrate that the ortho substituent causes a higher energy for isomer II, while crystal lattice energy calculations show that the values are almost equal for two isomers.