The beige essential oil, in the form of crystals at room temperature, was extracted from the dry roots of Mondiawhiteï(Hook. f.) Skeels by hydrodistillation with a yield of 0.50%. Analysis by gas chromatography (GC) and gas chromatography coupled by mass spectrometry (GC/MS) revealed the presence of a single constituent, the aromatic aldehyde, 2-hydroxy-4-methoxybenzaldehyde, an isomer of vanillin representing (99.85%) of the total essential oil. 2-Hydroxy-4-methoxybenzaldehyde was instantly converted to the brick-red colored 2-hydroxy-4-methoxybenzaldehyde 2,4-dinitrophenylhydrazone by the addition of 2,4-dinitrophenylhydrazine on 2-hydroxy-4-methoxybenzaldehyde, nucleophilic addition reaction catalyzed by surfuric acid with a conversion rate of 93%. Analysis of hydrazone by UV-visible spectrophotometry shows a wavelength at the absorption maximum of 362 nm. The UV-visible spectrophotometric method used for the determination of this hydrazone is convenient, rapid and economical. This conversion allows the chemical structure of 2-hydroxy-4-methoxybenzaldehyde to be changed by providing the formed 2-hydroxy-4-methoxybenzaldehyde 2,4-dinitrophenylhydrazone with additional biological, chemical and physical properties while enhancing its economic value. The 2-hydroxy-4-methoxybenzaldehyde 2,4-dinitrophenylhydrazone formed opens up the prospects of its diversified use in the fields of pharmaceutical, electrochemical, catalytic, polymer chemistry, environmental, energy, materials, biology and engineering.