Synthesis and spectroscopic analyses of metronidazole-naphthol derivative

Abstract

The synthesis of metronidazole-naphthol derivative (Sample 5) was achieved by the reduction of metronidazole (Sample 1) with zinc in aqueous solution of hydrochloric acid and diazotization of the reduced product (Sample 2) with aqueous solutions of NaNO₂ and HCl at a temperature range of 0 – 5^oC. Diazo-coupling of 2- Naphthol unto the diazonium salt of metronidazole gave rise to metronidazole-naphthol derivative. The synthesis produced a yield of 28.2 and 36.4% for Sample 2 (1- (2-Hydroxyethyl)-2-methyl-5-aminoimidazole) and Sample 5 respectively. The purity of samples 1, 2 and 5 were verified from their melting points of 158 – 160⁰C, 154 – 156⁰C, 145 – 146⁰C respectively. The colour variation of Samples 1, 2 and 5 were cream, light- brown and red respectively. The chemical structures and bonding of the samples were verified with the use of Ultraviolet / Visible spectroscopic analysis, results obtained shows a maximum wavelength of 217 – 236 nm, 514 – 571 nm and 500 – 545 nm for Samples 1, 2 and 5 respectively. Fourier transform infrared spectroscopic analyses (FTIR) were employed to confirm the functional groups in the compounds. The appearance of vibrational peaks at wavelengths of 3733.72 - 3627.33 cm^-1, 3218.04 cm^-1, 1464.71 cm^-1, 1362.24 – 1213.85 cm^-1 for amino (-N-H), hydroxyl (-OH), stretching (-CH2) and cyano (C-N) groups respectively signifies the presence of the proposed amino product of metronidazole (Sample 2) while the peaks at 3381.24 cm^-1 (-OH), 3099.11 (C-H), 1617.00 cm^-1 (C=C), 1533.85 ( -N=N-), 1474.79 (-CH2) and 1366.51 - 1239.15cm^-1(-C-N) confirms the structure of metronidazole-naphthol derivative (Sample 5).