Simple mixing scheme

Chromium trioxide (CrOs) immobilized on premoistened alumina affords efficient oxidation of benzyl alcohols to carbonyl compounds by simple mixing (Scheme 7). Remarkably, neither the over-oxidation to carboxylic acids nor the formation of tar, a typical occurrence in many CrOs oxidations, is observed. ... 

For water based adhesive blending, low shear/low speed mixers are used to minimize shearing, which can coagulate the emulsion. This tends to minimize foam formation. The blending procedure for a simple mixing scheme is as follows ... 

In the simple mixing scheme the density matrix used in construaing the next Fock matrix is composed of a combination of the two previous density matrices i.e.,... 

The EPR spectrum shows, in accordance with the XPS results, no feature that can be attributed to Ti centers. What is the nature of the radical observed in the EPR spectrum It might be thought that methyl radicals are the most natural products in the reduction of a mixed titaniiun-chlorine-methyl species according to the following simple reaction scheme ... 

Additional combinatorial variation sites allow the heterocyclic self-assembly units. Thus, it has been shown that heterocycles 11 and 14-17 can serve as A-analogous donor-acceptor ligands self-assembling with the T-analogous acceptor-donor ligands isoquinolone 12 and 7-azaindole 18 (Scheme 30) [92]. All combinations form the heterobidentate ligands exclusively upon simple mixing in the presence of a transition metal salt (proven by X-ray, NMR). 

The chemical entrainment method was used by Ono et al. (1979) to eliminate the nitro group in nitroalkene derivatives. On simple mixing with thiophenol and sodium sulfide in DMF, nitro aryl olefins substitute hydrogen for the nitro group (Scheme 5.9). 

Reduction ofimines using formates Ammonium formates and formic acid have been employed as reducing agents in the synthesis of secondary amines from imines. By simple mixing of the reagents and microwave irradiation without solvent, the amines were produced in good yields within 2.5-10 min (Scheme 4.28)51. 

A related series of 5-substituted-2-amino-oxadiazole compounds have also been prepared in a one-pot procedure using a microwave-assisted cyclisation procedure (Scheme 6.26)164. Rapid preparation of the pre-requisite ureas from the mono acyl hydrazines and various isocyanates (or the isothiocyanate) was easily achieved by simple mixing. The resulting products were then cyclo dehydrated by one of the two procedures either by the addition of polymer-supported DMAP and tosyl chloride or alternatively with an immobilised carbodiimide and catalytic sulphonic acid. Purity in most cases was excellent after only filtration through a small plug of silica but an SCX-2 cartridge (sulphonic acid functionalised - catch and release) could be used in the cases where reactions required additional purification. 

A laser whose frequency is unknown can be compared to a reference laser by heterodyne methods to high precision. Beat frequency measurements up to 2.5 THz in the visible spectrum have already been made. An alternative to simple heterodyne schemes is harmonic mixing by use of synthesis chains. 

For many applications, the basis sequence can be iteratively constructed from simplw tarting sequences (Tyko, 1990). MLEV-4-type super cycles RRRR or RRRR (Levitt et al., 1983) are examples of simple iterative schemes for the construction of basis sequences with vanishing effective fields from a starting sequence R, which is a (approximate) composite inversion pulse R. Here, the composite pulse R is identical to R, except that the phases of all square pulses are shifted by 180°. The MLEV-16 super cycle RRRR RRRR RRRR RRRR (Levitt et al., 1983) suppresses effective fields even better. MLEV-4- and MLEV-16-type supercycles are often used in the construction of broadband Hartmann-Hahn mixing sequences. In these sequences, an effective spin-lock field can be introduced by adding an uncompensated additional pulse after each complete supercycle (see Section X). 

Although in principle the simple scheme presented in Fig. 5.59 should provide TOCSY spectra, its suitability for practical use is limited by the effective bandwidth of the continuous-wave spin-lock. Spins which are off-resonance from the applied low-power pulse experience a reduced rf field causing the Hartmann-Hahn match to breakdown and transfer to cease. This is analogous to the poor performance of an off-resonance 180° pulse (Section 3.2.1). The solution to these problems is to replace the continuous-wave spin-lock with an extended sequence of composite 180 pulses which extend the effective bandwidth without excessive power requirements. Composite pulses themselves are described in Chapter 9 alongside the common mixing schemes employed in TOCSY, so shall not be discussed here. Suffice it to say at this point that these composite pulses act as more efficient broadband 180 pulses within the general scheme of Fig. 5.60. 

The process involves simple mixing of carbonyl compounds with 10% NaBH4 supported on alumina and exposure of the reaction mixture to microwaves in a household MW oven for 0.5-2 min (Scheme 2.2-43).The useful chemoselective feature of the reaction is apparent from the reduction of traus-cinnamaldehyde (cinna-maldehyde NaBH4-alumina, 1 1 mol equivalent) the olefinic moiety remains intact and only the aldehyde functionality is reduced in a facile reaction. 

Scheme 2.7 Simple mixing and heating led to a degradable bio-based polymer by reaction of 2-methylene-1,3-dioxepane and Tulipalin-A. (Reproduced from Ref. [40].)...

A very simple scheme which uses little computer time for one iteration is simple mixing. The (n + 1) guess Xn+i is simply given by... 

In the original Anderson mixing scheme, the (n + 1) guess x +i is given by x +i = g. More generally, the method can be combined with simple mixing... 

Figure 3.3 (a) Schematic drawing (not to scale) showing a typical mixed potential process of metal dissolution, using the example of Cu in Eqn (3.4). Transport of dissolved ions closes the (corrosion) current loop in the electrolyte. Reactions (3.9) and (3.10) are coupled here, as also noted in Figure 3.2(a—c). (b) A simple mixed potential scheme, commonly found in the corrosion literature to describe galvanic decay of an anode metal A in the bimetallic couple of A and C (cathode). The cation charge of A is z+. The cathode metal supports ORR, and the electrons necessary for this reaction come from the anode metal s dissolution. 

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