A method for cross-Aldol condensation of aliphatic aldehydes which is an industrially important reaction for the preparation of polyols has been developed based on phase transfer catalysts (PTC). The PTC promotes reaction between two aldehydes located in different phases of a mixture by transferring one reactant across the interface into the other phase, so that reaction can proceed efficiently. The PTC method is an alternative to commonly used alkali hydroxides, alkali carbonates, ion exchange resins and tertiary amine catalysts. For example, cross-aldolization of isobutyraldehyde and formaldehyde can be performed using PTC to form hydroxypivaldehyde, which is difficult to prepare with non-PTC catalysts because of the formation of different phases. The hydroxypivaldehyde formed is then converted into neopentylglycol by hydrogenation using metal catalyst. The aldol condensation reaction can be performed using 4 mole % equivalent of PTC at 20 oC with >99% selectivity of the aldol product. The catalyst is easily separated by extraction and it can be reused. The mechanism of PTC catalysis, including the affect of Time, agitation, exothermicity and advantages of PTC over the non-PTC catalysts from the industrial viewpoint will be presented.

Cross-aldol condensation of aliphatic aldehydes using phase transfer catalysts

246th National Meeting (2013)

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