Unraveling the reaction route and kinetics of 3-methyl-3-penten-2-one synthesis for synthetic ketone fragrances
BACKGROUND 3-Methyl-3-penten-2-one (3M3P) is an indispensable raw material used for the synthesis of OTNE (octahydrotetramethyl acetophenone), a synthetic ketone fragrance known by commercial trade names, such as Iso E Super® , which is one of the most important ingredients in perfumes. This work is the first to unravel the reaction route and kinetics for the synthesis of 3M3P via the cross-aldol condensation of acetaldehyde with butanone, catalyzed by the heterogeneous acidic ion exchange resin (NKC-9). RESULTS An effective method was developed to evaluate this complex reaction system: the reaction routes were determined experimentally from the product structures detected by Gas Chromatography Mass Spectrometry (GC-MS), and the significance of side reactions were evaluated by the Yoneda group contribution method. The major side reactions are the self-condensation of acetaldehyde (significant even under optimized reaction conditions) and the cross-aldol condensation of acetaldehyde with 3M3P (which could be effectively suppressed at high butanone-acetaldehyde molar ratio). The reaction kinetics was investigated at temperatures of 60–90 °C, catalyst mass fraction of 5 to 15%, and molar ratio of 5–20. At optimized reaction conditions, the yield of 3M3P was up to 90.85%, which is 2.4 times higher than that for the classic homogeneous catalysts (yield <38%). CONCLUSION Acidic ion exchange resin NKC-9 is a high-selective green catalyst for the cross-aldol condensation of acetaldehyde with butanone. Integrating experimental determination and thermomechanical analysis is an effective method to unravel the main reaction routes for a complex system. © 2020 Society of Chemical Industry (SCI)
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