Photochemical and photocatalytic degradation of 1‐propanol using UV/H₂O₂: Identification of malonate as byproduct

Abstract

1-propanol is a primary alcohol extensively used in the pharmaceutical, chemical, and food industries. It has been also found as a contaminant in the atmosphere and is considered a model compound to mimic the behavior and fate of aliphatic alcohols exposed to environmental conditions. In order to understand that role of relevant variables, this paper presents results obtained with a simple experimental set-up to investigate the reactivity of 1-propanol under mild oxidizing conditions. Coupling this system with CE-C⁴ D allowed the quantification of the carboxylic acids formed. For the described experiments, aqueous solutions of 1-propanol were placed inside a photoreactor and oxidized upon the addition of TiO₂ and/or H₂ O₂ . According to the described results, the addition of H₂ O₂ (0.1% w/w) was the most significant variable, roughly tripled the amount of carboxylic acids generated and led to the conversion of up to 70% of the initially available 1-propanol (1 mmol/L). More importantly, the reaction yielded the formation (within 10 min) of propionate (50 µmol/L), acetate (400 µmol/L), formate (50 µmol/L), and malonate (200 µmol/L). The latter is critically important because it represents the first example of the photochemical oxidation of both terminal carbons of the C₃ -chain of 1-propanol under mild conditions, and opens new avenues for the production of this important chemical building block.