Abstract:

Oxidation of alcohols is an important method to produce aldehydes and ketones, and is an important component in organic chemistry theory and practical teaching. Currently, oxidation of cyclohexanol to cyclohexanone is commonly introduced in practical undergraduate textbooks. The only experiment designed for the preparation of aldehydes from primary alcohols in current practical textbooks is using the oxidant H₂O₂ for the selective oxidation of benzyl alcohol to benzaldehyde at 90 ℃ in the presence of a catalytic amount of Na₂WO₄·2H₂O/(C₄H₉)₄NHSO₄. However, this reaction has low-yields, potential safety issues, and concerns with environmental pollution. Here, we present a practical alternative reaction involving the mixed catalytic system of Fe(NO₃)₃·9H₂O, 4-hydroxy-2, 2, 6, 6-tetramethyl-piperidinooxy (4-OH-TEMPO), and acetic acid (HOAc). This reaction allowed for a highly selective oxidation of benzyl alcohol to benzaldehyde with an isolated yield of up to 91% using O₂ as the oxidant and H₂O as the solvent under mild conditions. This new strategy for the selective oxidation of primary alcohols is a low-cost, and more importantly, highly efficient and green strategy. Additionally, several techniques such as thin layer chromatography, gas chromatography, flash preparative liquid chromatography, and ¹H NMR spectroscopy were used to detect and purify products, to improve experimental techniques, and to enhance the scientific literacy of undergraduate students.

Key words: Primary alcohol, Fe(Ⅲ) salt, Selective oxidation, Benzaldehyde, Green chemistry