The oxidation of isobutyraldehyde produces isobutyric acid and byproducts, such as isopropyl formate. A process of reducing the isopropyl formate byproduct and other byproducts in the oxidation of isobutyraldehyde is described. The process uses a carbonyl compound, such as acetone, to reduce byproduct levels in the resulting product. Process for use of static mixers in oxidation reactions of aldehydes are also provided.