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Issue 1, 2001
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The generation of concentration gradients usingelectroosmotic flow in micro reactors allowing stereoselective chemicalsynthesis

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The stereoselective control of chemical reactions has been achieved by applying electrical fields in a micro reactor generating controlled concentration gradients of the reagent streams. The chemistry based upon well-established Wittig synthesis was carried out in a micro reactor device fabricated in borosilicate glass using photolithographic and wet etching techniques. The selectivity of the cis (Z) to trans (E) isomeric ratio in the product synthesised was controlled by varying the applied voltages to the reagent reservoirs within the micro reactor. This subsequently altered the relative reagent concentrations within the device resulting in Z/E ratios in the range 0.57–5.21. By comparison, a traditional batch method based on the same reaction length, concentration, solvent and stoichiometry (i.e., 1.0∶1.5∶1.0 reagent ratios) gave a Z/E in the range 2.8–3.0. However, when the stoichiometric ratios were varied up to ten times as much, the Z/E ratios varied in accordance to the micro reactor i.e., when the aldehyde is in excess, the Z isomer predominates whereas when the aldehyde is in low concentrations, the E isomer is the more favourable form. Thus indicating that localised concentration gradients generated by careful flow control due to the diffusion limited non-turbulent mixing regime within a micro reactor, leads to the observed stereo selectivity for the cis and trans isomers.

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Publication details

The article was received on 16 Aug 2000, accepted on 20 Oct 2000 and first published on 19 Dec 2000

Article type: Paper
DOI: 10.1039/B006727J
Analyst, 2001,126, 11-13

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    The generation of concentration gradients using electroosmotic flow in micro reactors allowing stereoselective chemical synthesis

    V. Skelton, G. M. Greenway, S. J. Haswell, P. Styring, D. O. Morgan, B. H. Warrington and S. Y. F. Wong, Analyst, 2001, 126, 11
    DOI: 10.1039/B006727J

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