Reaction and Product Extraction

An application of this principle is in the telomerization of butadiene with ethylene glycol. One-phase reactions yield both mono- and ditelomers, while the two-phase system using a water/glycol phase containing a polar palladium catalyst avoids the 

The practicability of this concept will be demonstrated by two examples. In the first, the dimerization of butadiene to 1,3,7-octatriene in the presence of a catalyst containingg a palladium precursor and triphenylphosphine as well as the alcohol PhC(CF3)20H is carried out favorably in the solvent acetonitrile. The following 

The second example is the telomerization of phthalic acid with butadiene yielding bis(octadienyl) phthalates, which can be used as plastic softeners after hydrogenation. The polar solvent dimethyl sulfoxide contains the palladium catalyst formed from Pd(acac)2 and tris(p-methoxyphenyl)phosphite. This extraction uses isooctane as well [34]. 

The appropriate process described so far use only an aqueous catalyst solution, and no additional organic solvent is necessary. In the processes described in this section an organic nonpolar solvent is used as product extractant. Hydrocarbons, chlorinated hydrocarbons, or ethers are often chosen as nonpolar solvents. 

For this technique some examples are given in the literature. Baird [69, 70] describes the hydrogenation and the hydroformylation of olefins applying this two-phase system. The aqueous phase contains the soluble rhodium catalyst which is formed from norbomadienylrhodium chloride and AMPHOS nitrate (Ph2PCH2CH2NMe N03) the organic phase contains solvents such as methylene chloride, diethyl ether, or pentane, or the olefin, e.g., 1-hexene. This system is very favorable because only traces of rhodium (0.25 ppm) move into the organic layer, and the aqueous catalyst phase could be re-used in the reaction with little or no loss of activity, even after expsoure to air. 

An interesting new example is the two-phase telomerization of butadiene with ammonia, yielding octadienylamines [57]. When this reaction is carried out in homogeneous one-phase solution, a great amount of primary, secondary and tertiary amines is formed [56]. With the two-phase techniques using water, and toluene or pentane as the second phase, the consecutive reactions (Eq. 2) can be almost completely avoided, and the primary octodienylamines are the only main products. This reaction has not yet been realized industrially. 

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Figure 4 shows simultaneous reaction and product extraction, also called in situ extraction. The reaction of A and B runs in the reactor which contains the polar (e.g., aqueous) catalyst phase. The nonpolar extractant absorbs the organic products which are separated from the polar catalyst phase in the following separation step. The procedure is more costly because a further distillation is necessary in a third unit to separate the products from the low-boiling extractant, which is then recycled to the reactor. 

An important alternative is the successive reaction and product extraction procedure shown in Figure 5. First the reaction of A and B is carried out in a single polar homogeneous phase containing the catalyst. Downstream, the products are extracted with a nonpolar solvent or solvent mixture. In the third unit, the distillation, the low boiling extractant is distilled off and recycled to the extraction unit. Two examples will demonstrate the practicability of this concept. 

Fig. 6 Successive reaction and product extraction (after solvent distillation).

Many interesting biocatalytic reactions involve organic components that are poorly water-soluble. When using organic-aqueous biphasic bioreactor, availability of poorly water-soluble reactants to cells and enzymes is improved, and product extraction can be coupled to the bioreaction. Many applications in two-phase media can use the existing standard-type bioreactors, such as stirred-tank, fluidized-bed, and column reactors with minor adjustments. 

CAimHPFf ] [CgQimHPFe] and others K2[0s02(0H)4] NMO K3[Fe(CN)6] k2co3 Enantioselective dihydroxylation of olefins with H20 and t-BuOH as co-solvents detailed study on reaction parameters product extracted with Et20 activity and selectivity stable for 9 runs, then considerable decrease osmium contamination in the product < 7 ppb. [64] [65]... 

Figure 8.5 Visual vapour-liquid phase equilibrium observations of the reaction bulk, where liquid reaction bulk was in the contact with the solid biocatalyst and the upper phase was saturated with substrates and products, extracted by SC-COj.

Fig. 8 depicts mass indices S-1 and environmental factors E and gives an indication of the mass efficiency for the four routes A-D. The amounts of chemicals needed for the production of 1 kg HPB ester varied between approximately 40 kg and 105 kg. In all cases, the major components were water and the solvents needed for the reactions and/or extractions, a picture that is typical for fine chemical synthesis. Route D clearly had the lowest consumption of materials. The main drawback for the two biochemical routes A and B were the need for rather large amounts of water and solvents (for extraction), even though it has to be pointed out that these processes were not optimized. Comparable variations were observed for the substrate consumption, i.e., how much starting material was needed to produce 1 kg of HPB ester (see Fig. 8b). In this case, however, both the highest (C) and the lowest (D) consumptions were observed for the chemical routes. The...

Some economic aspects, including rhodium catalyst cost, are treated in section 8.2. Catalyst performance aspects are treated in sections 8.3 (activity, selectivity) and 8.4 (stability, loss routes for Rh and ligand). In 8.5 and 8.6, several commercial processes are described. Four generic, industrially used process types are described in 8.5, viz. processes using a stripping reactor, a liquid recycle, a two-phase reaction, and an extraction after a one-phase reaction. In 8.6, interesting, current developments in a few petrochemical product areas are shortly discussed. 

Another thing or two to remember when distilling is to wrap aluminum foil around the reaction flask. This will help stop heat loss so that things will distill quicker and at lower temperatures. Sometimes, if one is going to distill a solution that is just solvent and product, all that pure solvent that comes over first is perfectly reusable and should be saved for future extractions. 

Alkvl Azides from Alkyl Bromides and Sodium Azide General procedure for the synthesis of alkyl azides. In a typical experiment, benzyl bromide (360 mg, 2.1 mmol) in petroleum ether (3 mL) and sodium azide (180 mg, 2.76 mmol) in water (3 mL) are admixed in a round-bottomed flask. To this stirred solution, pillared clay (100 mg) is added and the reaction mixture is refluxed with constant stirring at 90-100 C until all the starting material is consumed, as obsen/ed by thin layer chromatographv using pure hexane as solvent. The reaction is quenched with water and the product extracted into ether. The ether extracts are washed with water and the organic layer dried over sodium sulfate. The removal of solvent under reduced pressure affords the pure alkyl azides as confirmed by the spectral analysis. ... 

A solution of benzyl indole-5-carboxylate(1.0g, 3.98 mmol) and methyl 4-(bro-momethyl)-3-methoxybenzoate (2.06 g, 7.97 mmol) in dry DMF (10 ml) was heated at 80°C for 24 h. The reaction solution was cooled, poured into water (100 ml) and the product extracted with EtOAc (3 x 75 ml). The extract was washed with water and brine and dried over MgSO, . The product was obtained by evaporation of the solvent and purified by chromatography on silica gel using 1 4 EtOAc/hexane for elution. The yield was 1.11 g (32%) and some of the indole (30%) was recovered unreacted. 

Potassium hydride (1 eq.) was washed with hexanes and suspended in anhydrous ether at 0°C. 7-Bromoindole was added as a solution in ether. After 15 min, the solution was cooled to — 78°C and t-butyllithium (2 eq.) which had been precooled to — 78°C was added by cannula. A white precipitate formed. After 10 min DMF (2 eq.) was added as a solution in ether. The reaction mixture was allowed to warm slowly to room temperature and when reaction was complete (TLC) the suspension was poured into cold 1 M H3PO4. The product was extracted with EtOAc and the extract washed with sat. NaHCOj and dried (MgS04). The product was obtained by evaporation of the solvent and purified by chromatography on silica gel (61% yield). 

Other uses include use as a reaction and extraction solvent in pharmaceutical production as an intermediate for the preparation of catalysts, antioxidants (qv), and perfumes and as a feedstock in the production of methyl isopropenyl ketone, 2,3-butanedione, and methyl ethyl ketone peroxide. Concern has also arisen at the large volume of exported MEK which has been covertly diverted and used to process cocaine in Latin American countries... 

Acylthiophenes. Manufacturing methods introducing the carboxaldehyde group into the 2- or 5-positions of thiophene and alkylthiophenes utilise the Vilsmeier-Haack reaction. To synthesize 2-thiophenecarboxaldehyde (Table 5), a controlled addition of phosphoms oxychloride to thiophene in /V, /V- dim ethyl form am i de is carried out, causing the temperature to rise. Completion of the reaction is followed by an aqueous quench, neutralization, and solvent extraction to isolate the product. 

Stannous Sulfate. Stannous sulfate (tin(Il) sulfate), mol wt 214.75, SnSO, is a white crystalline powder which decomposes above 360°C. Because of internal redox reactions and a residue of acid moisture, the commercial product tends to discolor and degrade at ca 60°C. It is soluble in concentrated sulfuric acid and in water (330 g/L at 25°C). The solubihty in sulfuric acid solutions decreases as the concentration of free sulfuric acid increases. Stannous sulfate can be prepared from the reaction of excess sulfuric acid (specific gravity 1.53) and granulated tin for several days at 100°C until the reaction has ceased. Stannous sulfate is extracted with water and the aqueous solution evaporates in vacuo. Methanol is used to remove excess acid. It is also prepared by reaction of stannous oxide and sulfuric acid and by the direct electrolysis of high grade tin metal in sulfuric acid solutions of moderate strength in cells with anion-exchange membranes (36). 

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