Synthesis, characterization, conformational study, and antioxidant activity of N-acylhydrazone derivatives

Lee, Charles Kuok Sui (2025) Synthesis, characterization, conformational study, and antioxidant activity of N-acylhydrazone derivatives. Final Year Project, UTAR.

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Abstract

A series of N-acylhydrazone derivatives (SB 1-SB 8) were successfully synthesized in yields ranging from 68% to 97% through the condensation of a carboxylic acid hydrazide with various benzaldehydes bearing different substituents. The structures of the synthesized compounds were confirmed by FTIR, 1H NMR, 13C NMR, DEPT-135, NOE, HMQC, and HMBC spectral analyses. Based on the relative configuration of the imine (C=N) double bond and the conformation of the amide [C(=O)–NH] bond, the C=N double bonds of the N-acylhydrazones were assigned the E configuration. Furthermore, the NMR data of all synthesized compounds indicated the presence of both cis and trans conformers. The population ratio of cis conformers ranged from 32% to 60%, while that of trans conformers ranged from 41% to 68%. The rotational barriers of the cis/trans conformers were determined to be between 73.47 and 77.81 kJ/mol. The antioxidant activity of the synthesized N-acylhydrazone derivatives was evaluated using the DPPH assay. Apart from SB 7, which exhibited weak antioxidant activity, the compounds did not demonstrate significant antioxidant properties.

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