Esterfication

For transesterification/esterfication, continuous reactors may be more attractive than batch reactors. This is particularly true if a distillation-column reactor can be adopted, as it tends to use a much lower ratio of reactants to drive the reaction to the desired degree of conversion, entailing lower energy lost. Even when metal alcoholates are used these can be recycled, eliminating problems faced in batch plants. Relative process costs may well approach 50% of those in batch plants. Higher purity, less plant down time, better process control, and improved yield are other attractive features of continuous plants (Braithwate, 1995). 

Heterogeneous Transesterification and Esterf cation Catalysts 333 MeOH HaSOj... 

The industrial synthesis of polyformaldehyde [poly(oxymethylene)] occurs by anionic polymerization of formaldehyde in suspension. For this the purification and handling of monomeric formaldehyde is of special importance since it tends to form solid paraformaldehyde. After the polymerization the semiacetal end groups have to be protected in order to avoid thermal depolymerization (Example 5-13). This is achieved by esterfication with acetic anhydride (see Example 5-7). As in the case of trioxane copolymers (see Sect. 3.2.3.2) the homopolymers of formaldehyde find application as engineering plastics. 

In esterfication, an alcohol reacts with a carboxylic acid to produce an ester and water. The resulting ester contains an alcohol part and an acid part. 

Draw the product formed from a Claisen reaction with the given esterfs) using OEt, EtOH. 

Goldberg, R., Morvan, C., Jauneau, A. and Javis, M.C. 1996. Methyl-esterfication, de-esterfication and gelation of pectins in the primary cell wall. In Pectins and Pectinases, J. Visser and A.G.J. Voragen, Amsterdam Elsevier, pp. 151-172. 

Arylamine— o-hydroxy sulfate esterf In an alkaline medium, arylamines are oxidized by the reagent to o-hydroxy sulfate ester salts. Thus a solution of 5 g. of N,N-dimethylaniline in 250 ml. of water, 400 ml. of acetone, and 30 ml. of 2N potassium hydroxide was stirred at room temperature during addition in 8 hrs. of... 

Ndayibagara, A. and P.A. Spear. Esterfication and hydrolysis of vitamin A in the liver of brook trout (Salvelinus fontinalis) and the influence of a coplanar polychlorinated biphenyl. Comp. Biochem. Physiol. 122C 317-325, 1999. 

Homologation of methanol catalysed by 1 and 2 in presence of iodide promoter hydroiodic acid (entry Nos. 1 and 3), gave dimethyl ether selectively and while in the presence of water along with hydroiodic acid ( entry Nos. 2 and 4), both catalyst systems favoured the formation of acetic acid and dimethyl ether as the products. Catalyst 2 also gave methyl acetate a product of esterfication of acetic acid by methanol. Homogeneous catalyst 1 is at least two times more reactive than 2 in presence of water, however, catalyst 2 is more selective towards the formation of acetic acid (80%). 

Figure 3. Typical chromotograms for pectins with 0, 37 and methylation esterfication.

For the sake of completeness, it may be added that sulfur dioxide has also been used as the catalyst in hydration (3 ) and dehydration (S3) reactions, in the curing of phenol-formaldehyde resins (34), in esterfication... 

One example in which industrial chemists have to deal with suspensions is add scavenging. Browsing organic textbooks one will find numerous reactions which liberate acids that have to be scavenged in order to prevent decomposition of the product or other side reactions. Equations (1) to (6) show some common acid -liberating reactions, namely esterfication, elimination, phosphorylation, sul-furylation, silylation, and deprotonation, respectively. 

Esterfication of acetic acid with ethylene, propylene, butenes and isobutylene... 

As shown in Table 3.2, 5% BTCA in the presence of 10% SHP and 0.1% TiO (as a cocatalyst) was nsed, and the addition of TiO as a cocatalyst further increased WRA by 58.5%. This was becanse both TiO and SHP accelerated the catalytic reaction throngh the formation of ester bonds between the cyclic anhydride ring and the hydroxyl gronp of cellulose. The improvement of WRA by the addition of TiO in the BTCA treatment was probably dne to the nniqne photocatalytic properties of TiO, which is a kind of N-type semicondnctor. The hydroxyl radical (-OH) and snperoxide anion (-0 -) formed may have acted as catalysts to accelerate the formation of anhydrides from poly (carboxylic) acids. Fnrthermore, the effect of hydroxyl radical (-OH) and superoxide anion (-O -) on the increase of charge localization of the sohd cellulose medium in which esterfication and cross linking occur may also have been significant. Therefore, WRAs of cotton fiber treated with 5% BTCA, 10% SHP, and 0.2% TiO further increased to 61.3% compared with those of the untreated cotton fabric. The increment was proportional to the increase of TiOj from 0.1 to 0.2% in the BTCA treatment bath (Lam et al., 2011). 

Hasanoglu, A., Salt, Y., Kele er, S. and Din9er, S. 2009. The esterfication of acetic acid with ethanol in a pervaporation membrane reactor. Desalination 245 662-669. 

Hydrolysable tannins are derived from simple phenolic acids, particnlarly gallic acid, which is linked to a sngar by esterfication. The gallic acid gronps are nsnally bonded to form dimers snch as ellagic acid. 

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