Abstract

A series of previously unavailable derivatives of coumarins were synthesized via the reaction of 4-hydroxycoumarin with ethyl bromoacetate which were then cyclized with thiosemicarbazide. The structures of all synthesized compounds were confirmed by nuclear magnetic resonance (NMR) and infra red (IR) spectroscopic techniques in addition to the use of elemental analysis method (CHN). Selected optimized geometrical parameters, have been reported and highest occupied molecular orbital (HOMO) - lowest unoccupied molecular orbital (LUMO) energies and structures were elucidation.

Key words: DFT, HOMO-LUMO energies, 4-hydroxycoumarin, ethyl bromoacetate, nitrous acid, thiosemicarbazide

Abbreviation

NMR, Nuclear magnetic resonance; IR, infra red; DFT, density functional theory; HOMO, highest occupied molecular orbital; LUMO, lowest unoccupied molecular orbital; TLC, thin layer chromatography; m.p., melting point; FT-IR, Fourier transform infrared spectroscopy.