Influences of the Reaction Medium

The reaction medium represents another important factor for anisotropic nanocrystal growth, as the viscosity and boiling temperature can influence chemical reduction at a specific crystal facet, leading to different growth rates for different facets [25, 28, 29, 39]. In fact, hexagonal nanoplates that were produced almost quantitatively in an aqueous solution totally disappeared in THF solution. Rather, faceted isotropic particles were dominant under the same reductant. 

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At low temperatures, the nonenzymatic reaction is reduced to a larger extent than the enzymatic reaction. The mass transfer rate is reduced to a smaller extent. Mass transfer limitation is required for high enantiomeric excess and determines the conversion rate. Therefore, the volumetric productivity decreases at lower temperatures. The equilibrium constant is considerably higher at low temperatures, resulting in a higher extent of conversion or a lower HCN requirement. Both the volumetric productivity and the required enzyme concentration increase by increasing the reaction temperature and aqueous-phase volume while meeting the required conversion and enantiomeric excess [44]. The influence of the reaction medium (solvent and water activity) is much more difficult to rationalize and predict [45],... 

Quantitative analysis of the influence of the reaction medium - It may be reasonably expected... 

By heating the mixture in a buffer solution at greater than 100° C in an autoclave the question about the influence of the reaction medium on number and kind of volatiles should be answered. The answer, indeed, is very simple most compounds formed in the autoclave have been identical to the volatiles after roasting the mixture. Consequently, the reaction temperature is the most decisive factor for the formation of thermal aroma compounds. 

Another noticeable characteristic of captodative olefins is the influence of the reaction medium. The stabilizing effect of solvent on the persistency of a captodatively radical has been reported experimentally for the bond homolysis of bis(3,5,5-trimethyl-2-oxomorpholin-3-yl) [111], but was not found for the 2,3-diphenyl-2,3-dimethoxysuccinonitrile homolysis [112]. Theoretically the solvent-assisted stabilization las been predicted for the captodative substituted nitriles in solvent with large dielectric constants [113-114], Table 16 illustrates the solvent effect on the spontaneous thermal polymerizations [115]. The polymer yields are... 

The influence of the reaction medium on azo coupling reactions has been reviewed by Zollinger et al. [506]. 

Rencurosi A, Lay L, Russo G, Caneva E, Poletti L (2005) Glycosylation with trichloroacetimi-dates in ionic liquids influence of the reaction medium on the stereochemical outcome. J Org Chem 70 7765-7768... 

Figure 12.5-13. Influence of the reaction medium on peptidase-catalyzed peptide synthesis.

Fig. 6.5.11 Influence of the reaction medium on RAMA-catalyzed aldol additions of DHAP to A-Cbz-aminoaldehydes. Molar percentage conversion to product in water/Ci4li4/hexadecane (i.e. oil) 90/4/6 wt % (black bars) and dimethylformamide/water 1 4 mixture (grey bars)...

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