Cocrystallization reaction

Cocrystals can also be prepared in situ in covered depression slides on the polarized optical light microscope or Raman microscope by adding a small drop of solvent to the solid reactants. This has been shown for cocrystals of CBZ NCT with ethanol, ethyl acetate or 2-propanol. Photographs obtained through the polarized light microscope are shown in Fig. 22. These images show cocrystal formation in less than three minutes after solvent addition. In this case, the cocrystallization reaction proceeds by a similar pathway to those of macro-phase suspensions described above. In micro-phases the solvent added must allow for dissolution of both reactants so that concentrations in... 

The reaction between Bul2Si(OH)2 and Cl4Sn affords, after workup and crystallization from CH2C12, the tin complex 51 containing a bridging But2Si(OH)2 molecule, which is cocrystallized with (H0Bu 2Si)20, the structure of which is described in Section IV,D,1 (272). 

High resolution crystallographic studies have demonstrated that AspAT has open and closed conformations. Upon the binding of a substrate which favors the closed conformation, the small domain rotates so that the active site residues are brought closer to the substrate moiety. This movement of the small domain is important for initiation of the catalytic reaction. Therefore, the closed conformation is believed to represent the functional states of the enzyme.291 Three distinct crystal forms of mAspAT were analyzed, namely triclinic crystal for open conformation, monoclinic and orthorhombic crystals for closed conformation. The enzymes cocrystallized with substrate analogs seemed to have a tendency to assume the closed conformation.28 291 The order of this tendency was shown to be apoenzyme1 > PLP form of the enzyme > PMP form of the enzyme. 

Obviously, lithiation was not complete since 1 out of 3 equiv. of the starting material is still present. The minor modification of stirring the reaction mixture for 4 d instead of 24 h yielded the completely metallated product 2 as shown in Fig. 2. Crystallization is not necessarily providing pure products and the use of this cocrystallized material 1 is one of the reasons for not very clear reactions which have been reported with (Me3Si)3SiLi(THF)3. 

Decarbonylation and Decarboxylation - The photochemical reactions between carboxylic acids such as formic and trifluoroacetic acid and silica surfaces have been studied. The irradiation of diphenylacetic acid in acetonitrile with acridine results in the decarboxylation and the formation of the adduct (102). When the two achiral compounds, acridine and diphenylacetic acid, are cocrystallized a chiral two component molecular crystal is obtained in which the components are present in a 1 1 ratio. Both (—)- and (+)- crystals can be obtained. This crystalline material is photochemically reactive and irradiation brings about decarboxylation and formation of the adduct (102) with an ee of 35%. This compound is accompanied by a low yield of (103) which is formed exclusively on irradiation of the reactants in acetonitrile solution.Photochemical decarboxylation can be brought about by the irradiation of benzilate (104)/ methyl viologen pairs. ... 

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