Solvent, participating, preparation

The examples of this section summarise the recent application of the solvent-drop grinding approach to solid-state cocrystal preparation. The approach has been shown in certain instances to provide for either acceleration of CO crystallisation kinetics or selection of a particular polymorph via solid-state grinding. The approach is attractive, as it appears to incorporate some of the beneficial aspects of solvent participation while maintaining an essentially green, eco-friendly process. 

In the presence of iron catalysts at temperatures above 300°C, the rare earth chlorides react with alkali cyanides to give R(CN)3. The product is unstable, however, and disproportionates to cyanamide (Ferret and Banderet, 1937). Solid R(CN)3 can be prepared by the reaction between LiCN and RBtj in tetra-hydrofuran solution. Chemical analysis of the product has shown, however, that the solvent participates in the reaction and that the correct composition is R(CN)3 2THF (Rossmanith, 1966). 

Calibration data (e.g., linearity or sensitivity) are not discussed in detail between laboratories, but a typical calibration starts with 50% of the lowest fortification level and requires at least three additional calibration levels. Another point of calibration is the use of appropriate standards. In 1999 a collaborative study tested the effect of matrix residues in final extracts on the GC response of several pesticides.Five sample extracts (prepared for all participants in one laboratory using the German multi-residue procedure) and pure ethyl acetate were fortified with several pesticides. The GC response of all pesticides in all extracts was determined and compared with the response in the pure solvent. In total, 20 laboratories using 47 GC instruments... 

Besides solvation, a solvent can also participate in entrainment of ion-radical transformations. The reaction between tertiary aliphatic nitro compounds and the sodium derivative of nitromethane, NaCH2N02, is an example (Kornblum and Erickson 1981). To prepare NaCHjNOj, nitromethane is treated with sodium hydride. Then a tertiary aliphatic nitro compound is introduced into the solution formed. Several organic solvents were probed and CHjSOjCHj (DMSO) turned out to be the most effective. Kornblum and Erickson (1981) attributed this result to the formation of small amounts of NaCH2SOCH3 (sodium dimsyl) that was produced from DMSO as a result of its reaction with sodium hydride. Sodium dimsyl acts as a powerful one-electron reducer that induces the following chain anion-radical process ... 

Interestingly, the dinnclear Cu complexes 12 and 13 (Scheme 6) could be recovered from the crude reaction mixtures or, alternatively, prepared independently by mixing eqnimolar amonnts of ligands and CnBr-SMe2 in an appropriate solvent. It was established that these Cn complexes participate in the catalytic cycle, as the reaction of methyl croto-nate and EtMgBr with the independently prepared (or recovered) complexes (0.5 mol%) afforded the prodnct with the same yields and enantioselectivities as previously obtained with the complexes prepared in situ. 

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