Cosolvency disadvantages

These redox chain reactions, which cycle iron(II) and iron(III), have advantages over methods that use stoichiometric quantities of oxidants because the hydroxymethyl radical is also a good reductant and, at high oxidant concentrations, it may be oxidized more rapidly than it adds to (72). The disadvantage of this type of reaction is that the initial radical is generated by a relatively non-selective hydrogen atom abstraction reaction. To be efficient, the H-donor must be used in large excess it is often a cosolvent. Nonetheless, this is a very practical method to prepare hydroxyalkylated and acylated heteroaromatic and related derivatives. 

The early Organic Syntheses procedure for the synthesis of hexan-l-ol [24] is typical, but suffers from the disadvantage of using benzene as a cosolvent, as... 

In the literature, the thermodynamic advantages of cosolvent addition have been emphasized however, the effect of cosolvents on other aspects of the process, such as mass transfer, overall cost, and product/residue properties, has not been considered in depth. Benefits of cosolvent addition must be balanced against its disadvantages for a specific application. Cosolvent introduction and solvent recovery (separation of the cosolvent from the extract, SCF, and solids residue) increase the complexity of process design. As well, an increase in solvent loading may result... 

The disadvantage of this process is that both the active ingredient and the shell material must be very soluble in supercritical fluids. In general, very few polymers are soluble in supercritical fluids such as CO2. The solubility of polymers can be enhanced by using cosolvents or nonsolvents. This increases the solubility in supercritical fluids, but the shell materials do not dissolve at atmospheric pressure. 

To increase the hpophihc character, cosolvents can be added to the classical RCH/RP system. Solvents like methanol, ethanol, polyethylene glycol strongly increase the hydroformylation rate [8]. The potential disadvantages of these cosolvents are leaching into the organic phase and their reactivity towards acetals. Leaching of catalyst and hgand seems to be no problem, provided that certain concentrations of cosolvents are not... 

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