Cis-Trans Isomerism of Double Bonds

The products of reactions generating double bonds can exhibit positional isomerism, as rotation of the moieties, given before the reaction, is now prevented. This is usually referred to as cis/trans or, as a complementary description, Z/E isomerism. There are first hints that cis/trans or ZjE ratios of the products with micro-reactor processing differ from the corresponding data for conventional processing. 

An example of such an impact is the Wittig reaction. For the formation of double bonds from 2-nitrobenzyltriphenylphosphonium bromide and methyl 4-formyl-benzoate, it was determined that the ratio of cis and trans products (Z/F ratio) can be changed by simply adjusting the voltages in an electroosmotic-flow driven chip 

For a Michael addition, however, the same isomeric ratio (99% trans 1% cis) was observed for micro-reactor and batch operations [151]. 

The results clearly show that more results are needed to confirm the validity of the impact of micro reactors on the regioisomerism of substituted aromatics. Also, an explanation is needed of whether the effect can be confirmed. 

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