Etherification with simultaneous

The most important examples of reactive separation processes (RSPs) are reactive distillation (RD), reactive absorption (RA), and reactive extraction (RE). In RD, reaction and distillation take place within the same zone of a distillation column. Reactants are converted to products, with simultaneous separation of the products and recycling of unused reactants. The RD process can be efficient in both size and cost of capital equipment and in energy used to achieve a complete conversion of reactants. Since reactor costs are often less than 10% of the capital investment, the combination of a relatively cheap reactor with a distillation column offers great potential for overall savings. Among suitable RD processes are etherifications, nitrations, esterifications, transesterifications, condensations, and alcylations (2). 

After the raw stock is prepared and the equipment is checked for her-meticity, the etherification of silicon tetrachloride is started. The process is carried out in etherificator 6, which is a cast iron enameled apparatus with a jacket. From batch boxes 2 and 3 the etherificator is simultaneously filled with anhydrous ethyl alcohol and silicon tetrachloride. Apart from anhydrous alcohol, the etherificator receives recirculating ethyl alcohol from batch box 4. In certain volume ratios (usually from 1 2.2 to 1 2.3) silicon tetrachloride and alcohol enter through siphons the lower part of the etherificator. The temperature of the process (30-40°C) is maintained by regulating the supply of the components. The pressure in the apparatus should not exceed 0.015-0.016 MPa. 

The use of RD in the manufacture of other ethers such as ETBE, TAME, and so on, has been demonstrated to be beneficial and several patents and investigations have emerged [3, 4]. UOP describes a process for the manufacture of DIPE (di-isopropyl ether), which uses propylene and water feedstock. It is a two-stage RD process associated with simultaneous hydration and etherification [5]. The ethers, being the heaviest components, are collected in the bottom stream. 

Barium hydroxide dimethylf ormamide Reactions with simultaneous etherification and esterification Goumarin ring opening Benzilic acid rearrangement Partial formation of ketals... 

Modification of urea-formaldehyde resins with other reagents gives rise to a number of useful materials. For example, co-condensation of urea-formaldehyde and a monohydric alcohol in the presence of small quantities of an acidic catalyst will involve simultaneous etherification and resinification. n-Propanol, n-butanol and isobutanol are commonly used for this purpose. As an example n-butanol will react with the methylol urea as shown in Figure 24.4. 

While the notion that the alkoxides derived from aliphatic alcohols are poor nucleophiles toward 7r-allylmetal complexes has prevailed over the years, much progress made in the recent past has rendered the transition metal-catalyzed allylic alkylation a powerful method for the O-allylation of aliphatic alcohols. In particular, owing to the facility of five- and six-membered ring formation, this process has found extensive utility in the synthesis of tetrahydrofurans (THFs) (Equation (29))150-156 and tetrahydropyrans (THPs).157-159 Of note was the simultaneous formation of two THP rings with high diastereoselectivity via a Pd-catalyzed double allylic etherification using 35 in a bidirectional synthetic approach to halichondrin B (Equation (30)).157 The related ligand 36 was used in the enantioselective cyclization of a Baylis-Hillman adduct with a primary alcohol (Equation (31)).159... 

The alkoxylation of these structures, having carboxyl groups and hydroxyl groups, is a self catalysis process, catalysed by the acidic -COOH groups. Two simultaneous reactions take place the esterification of carboxyl groups with PO (reaction 16.14) and the etherification of hydroxyl groups (reaction 16.15) [34]. 

For etherification of alkali-sensitive substances such as polyphenols it is advisable to treat the derived acetate with dimethyl sulfate and alkali (if necessary, with addition of acetone), which achieves simultaneous hydrolysis... 

The manufacturing process for partially alkylated amino formaldehyde resins consist of two consecutive reactions. The first reaction is the methylolation (hydroxy-methylation) of an amino compound such as urea, melamine, or benzoguanamine with formaldehyde and can be carried out under basic or acidic conditions. Hydroxy-methylation under acidic conditions leads to simultaneous alkylation and polymerization of the amino resin. The second reaction, alkylation (or etherification), is carried out under acidic conditions. 

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