The Oxidation of 4-(4-Formylphenoxy) Phthalonitrile to 4-(4-Carboxylphenoxy) Phthalonitrile at Ambient Conditions

Abstract

The substituted phthalonitriles have been used to prepare soluble phthalocyanine species in recent years. One of the most used phthalonitrile derivatives for the target product is 4-nitrophthalonitrile. In this study 4-(4-formylphenoxy) phthalonitrile was prepared as the substituted phthalonitrile derivative by the nucleophilic substitution reaction of para-hydroxybenzaldehyde with 4-nitrophthalonitrile. During the crystallization of the product by slow evaporation technique, it readily self-oxidized to 4-(4-carboxylphenoxy) phthalonitrile at ambient condition open to air. The crystal structure of the molecule was determined by XRD technique. The molecule crystalizes at triclinic space group P-1 and the unit cell parameters of crystal are a=6.3591 (10) Å, b=7.5464 (11) Å, c=13.819 (2) Å, α=88.434 (11)°, β=87.942 (12)°, γ=80.111 (12)° and Z=2. The crystal structure has intermolecular O―H∙∙∙O, C―H∙∙∙N and C―H∙∙∙O hydrogen bonds. In addition to these hydrogen bonds, C—N∙∙∙Cg and Cg∙∙∙Cg interactions are present between molecules. In the crystal, intermolecular O―H∙∙∙O hydrogen bonds occur between molecular units in a dimeric molecular form. Molecular structure, vibrational frequencies and 1H and 13C NMR chemical shifts of the target compound have been calculated by using B3LYP method with 6-311++G(d, p) basis set, as well.