Crystallisation solvents

Unlike processed vegetable fat the composition of butter can only be altered by fractionation (typical fatty acid compositions of milk fats are given in Tables 3.5 and 3.6). It is possible to fractionate butter by a number of methods, either using solvents (such as acetone or alcohol) or by vacuum distillation or slow crystallisation. Solvent fractionation can be used to produce well defined fractions but has certain disadvantages ... 

Figure 2.4.3 View of (a) a ladder coordination used as the crystallisation solvent, with the polymer, [Zn2(N03)4(3-pytz)3] , prepared when MeOH molecule coordinating the metal center using an EtOH or PrOH as crystallisation resulting in the formation of a hydrogen-...

In this instance, the exact proportions of the resolving agent and 8 and the purity of the crystallisation solvent were important in getting good results.3 After one crystallisation, the ee of the salt was about 50% but this improved by 10-15% with each recrystallisation and reached >99% after five recrystallisations. By then the yield had dropped to 30% from a theoretical maximum of 50%. For the next stage in their synthesis, they really needed the Boc derivative (5)-(+)-10 so the salt was directly converted to 10 in >99% ee on a 50 g scale. You will see later in this chapter that an enzyme can be used to do the same resolution. 

Compound M.p. [or b.p.l C. Crystal form (and crystallisation solvent) References... 

With the set-up it is possible to study the effect of solvent additives (eg foaming control, corrosion/degradation inhibitors). Therefore, the design of the pilot is such that differeut, uou-crystallising, solvent mixtures and modified types, both state-of-the-art chemical solvents and high load and activated solvents, can be tested. 

The crystallisation solvent is also an impurity and is present at very high concentrations around the crystal. Any of the mechanisms described for other impurities may also apply to the solvent and can produce similar changes in crystal habit. Finally, the interaction between solvent and crystal surface can change the surface energetics of the crystal faces due to the differential binding energies of solute and solvent on the different surfaces [58]. 

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