Mixing-sensitive reactions reaction schemes

The intensive mixers mentioned above are illustrated in Figure 9.3, together with others proposed in the literature in general they have been well characterized in terms of internal hydrodynamics and mixing performances, either by flow visualization techniques or using chemical methods, by mixing sensitive competitive reaction schemes computational fluid dynamics also supplied much information. 

Figure 5.15. Two examples of age-based micromixing models. In the top example, it is assumed that fluid particles remain segregated until the latest possible age. In the bottom example, the fluid particles mix at the earliest possible age. Numerous intermediate mixing schemes are possible, which would result in different predictions for micromixing-sensitive reactions. 

O Donnell et al have examined benzophenone-derived glycine acetate (85) as a glycine cation equivalent. Higher order mixed cuprates [R2Cu(CN)Li2] react with (85) to afford alkylated Schiff base (86) in moderate yields. The reaction is sensitive to reaction conditions and reduction competes with or-ganometallic addition. Hydrolysis of (86) provides access to aryl- or alkyl-substituted amino acids (87 Scheme 16). 

Mesoionic 4-amino-l,2,3,5-thiatriazoles constitute the only class of mesoionic 1,2,3,5-thiatriazoles known. They are prepared by the reaction of l-amino-l-methyl-3-phenylguanidine with approximately 2 equivalents of thionyl chloride with pyridine as solvent (88ACS(B)63>. They are obtained as the yellow 1 1 pyridine complexes (17). The dark-violet mesoionic 1,2,3,5-thiatriazole (18) was liberated on treatment with aqueous potassium carbonate (Scheme 3). The structure is established on the basis of elemental analysis and spectroscopic data. In particular, the IR spectrum is devoid of NH absorptions. Compound (18) exhibits a long-wavelength absorption at 463 nm in methanol. When mixed with an equivalent amount of pyridinium chloride, complex (17) is formed and the absorption shifts to 350 mn. The mesoionic thiatriazoles are sensitive towards mineral acids and aqueous base and although reaction takes place with 1,3-dipolarophiles such as dimethyl acetylene-dicarboxylate, a mixture of products were obtained which were not identified. 

The first borinate-transition metal complex to be prepared was actually the first known derivative of borin. Bis(cyclopentadienide)cobalt (94) reacts with organic halides and was analogously found to react with boron halides in a redox reaction to give (95), followed by an insertion to yield (cyclopentadienide)(borinato)cobalt (97) (72CB3413). The product composition depends on the ratio of reactants. Compound (97) is the main product (80% yield when R = Ph, X = Br) when the molar ratio between (94) and the boron halide is 2.5 1. A second and slower insertion occurs to give (28) when (97) is treated with another equivalent of the boron halide (Scheme 13). Compounds (28), (29) and (97) have one electron more than predicted by the 187r-electron rule for transition metal complexes. They are red in colour and, of course, paramagnetic. The mixed complexes (97) are thermally labile, in contrast to (28) and (29), which can be heated to 180 °C and sublimed at 90 °C. Their ionization potentials are low and the complexes are sensitive to air. 

As a result of the high electron density around the Re in Re(NR")3R complexes, the NR groups are extremely sensitive to hydrolysis and protonation. This type of reaction occurs with HCl, catechol, or pyHCl and opens a new route into Re(NR )2RxX3 x complexes and from these into the mixed alkyls Re(NR )2RxR3 j as exemplified in Scheme 18. 

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