Effect of molecular and crystal structure ofN-naphthylurethanes (carbamates) on their IR spectra

A comparative analysis of the IR spectra in the region of 3000–400 cm⁻¹ of four urethanes (methyl-(N-(1-naphthyl) carbamate, ethyl-N-(1-naphthyl) carbamate, dimethyl-N,N′-(1,5-naphthylene) dicarbamate, and diethyl-N,N′-(1,5-naphthylene) dicarbamate) with known molecular and crystal structures was carried out. The assignment of the bands related to the vibrations of the urethane and naphthyl fragments was refined on the basis of the study of the crystalline samples, melts, solutions, and deuterated analogs. The effect of the degree of conjugation of the urethane group with the naphthalene ring on the Amide II vibration frequency in the crystals was shown. It was suggested that the stretching vibrations of the C(Ar)−N bond in naphthylurethanes (unlike aliphatic derivatives) make a considerable contribution to the Amide II vibration, while the planar deformation vibration of the N−H bond was proved to be more significant for Amide III than for Amide II. In addition, strong nonspecific intermolecular interactions in the crystal can weaken valent bonds. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 300–303, February, 1998.