Ethanol esterification

Another appHcation of 4-chlorophenol is in the synthesis of a dmg, ethyl a, a-dimethyl-4-chlorophenoxy acetate [637-07-0] (60), used as a cholesterol-reducing agent. This synthesis involves reaction with acetone and chloroform, followed by ethanol esterification. 

A mechanism similar to that proposed by Mochida for the above-mentioned group of catalysts, though not so explicitely formulated, might also be valid for acetic acid—ethanol esterification over a H3P04/C catalyst [416]. According to the author, the adsorbed acid in a polymolecular film on the surface of the catalyst reacts with protonated molecules of the adsorbed ethanol. 

It follows from all the above considerations that the acidic character of the surface is necessary for the esterification reaction. This view is supported by the parallel found by some workers [405,406] between the rate of esterification and that of other typical acid-catalysed reactions. A linear correlation was established between the rate of acetic acid—ethanol esterification and that of deisopropylation of isopropylbenzene on a series of silica—alumina, alumina—boria and alumina catalysts [406] a similar relation was found between the rate coefficient of the same esterification reaction and the cracking activity of a series of silica—alumina catalysts prepared in a different way [405]. 

Considerably fewer kinetic studies were performed with reactants in the vapour phase than in the liquid phase. The second-order rate equation was only used for acetic acid—ethanol esterification at 130°C and 175° C on a KU-2 standard ion exchanger [444,445]. A semiempirical second-order rate equation with slight inhibiting effect of reaction products, viz. 

Table 4.9. Input Data for Ethanol Esterification. [Adopted from Mujtaba and Macchietto, 1997]...

Figure 4.8. Distillate Composition Profile for Ethanol Esterification...

Mujtaba and Macchietto (1997) proposed a new and an alternative technique that permits very efficient solution of the maximum profit problem using the solutions of the maximum conversion problem already calculated. This is detailed and explained in the following using again the ethanol esterification example presented in the previous section. 

The new technique is illustrated below with the same example (ethanol esterification) and using the results of the maximum conversion problem. For x D = 0.70, Mujtaba and Macchietto (1997) used 5th order polynomials to fit the data presented in Figures 9.3 and 9.5 a 3rd order polynomial to fit the data in Figure 9.4 and a Is1 order polynomial to fit the data in Figure 9.6 respectively. The resulting curves and the polynomial equations are shown in Figures 9.9-9.12. 

Fischer esterification is an equilibrium, and typical equilibrium constants for esterification are not very large. For example, if 1 mole of acetic acid is mixed with 1 mole of ethanol, the equilibrium mixture contains 0.65 mole each of ethyl acetate and water and 0.35 mole each of acetic acid and ethanol. Esterification using secondary and tertiary alcohols gives even smaller equilibrium constants. 

FIGURE 10.23 (See color insert following page 588.) Ethanol esterification with acetic acid comparison performances of different... 

Lact. plantamm and other Lactobacillus Streptococcus, Ent faecium (20 strains) in vitro ester synthesis by cell extracts from triglycerides plus ethanol (alcoholysis) and fatty acid plus ethanol (esterification) alcoholysis higher activity in Ent. faecium compared to Lact, with great strain-to-strain variations (factors of 7 and 30 within strains of Ent. faecium and Lact. plantarum, respectively) esterification most strains active great intraspedes variability (factes of 60 and 20 within strains of Ent faecium and Lact. plantamm, respectively) (Uuetal. 1998,2003 Abeijon Mukdsi et al. 2009)... 

The crude product is evaporated to dryness and then heated with a mixture of ethanol and sulphuric acid the cyano group is thus hydrolysed giving malonic acid, which then undergoes esterification to give diethyl malonate. 

Ethyl nicotiiiate may be prepared either by direct esterification of the acid with ethanol and sulphuric acid, followed by pouring into water and rendering ammoiilacal or by interaction of the acid with thionyl chloride, followed by reaction of nlcotiiiyl chloride hydrochloride with ethanol and subsequent neutralisation. 

Acetic anhydride acetylates free hydroxyl groups without a catalyst, but esterification is smoother and more complete ia the presence of acids. For example, ia the presence of -toluenesulfonic acid [104-15-4], the heat of reaction for ethanol and acetic anhydride is —60.17 kJ/mol (—14.38 kcal/mol) (13) ... 

Esterifica.tlon. The process flow sheet (Fig. 4) outlines the process and equipment of the esterification step in the manufacture of the lower acryflc esters (methyl, ethyl, or butyl). For typical art, see References 69—74. The part of the flow sheet containing the dotted lines is appropriate only for butyl acrylate, since the lower alcohols, methanol and ethanol, are removed in the wash column. Since the butanol is not removed by a water or dilute caustic wash, it is removed in the a2eotrope column as the butyl acrylate a2eotrope this material is recycled to the reactor. 

Most large-scale industrial methacrylate processes are designed to produce methyl methacrylate or methacryhc acid. In some instances, simple alkyl alcohols, eg, ethanol, butanol, and isobutyl alcohol, maybe substituted for methanol to yield the higher alkyl methacrylates. In practice, these higher alkyl methacrylates are usually prepared from methacryhc acid by direct esterification or transesterification of methyl methacrylate with the desired alcohol. 

Esterification. Esters are formed by the reaction of ethanol with inorganic and organic acids, acid anhydrides, and acid halides. If the inorganic acid is oxygenated, eg, sulfuric acid, nitric acid, the ester has a carbon—oxygen linkage that is easily hydrolyzed (24—26). 

There are two main processes for the synthesis of ethyl alcohol from ethylene. The eadiest to be developed (in 1930 by Union Carbide Corp.) was the indirect hydration process, variously called the strong sulfuric acid—ethylene process, the ethyl sulfate process, the esterification—hydrolysis process, or the sulfation—hydrolysis process. This process is stiU in use in Russia. The other synthesis process, designed to eliminate the use of sulfuric acid and which, since the early 1970s, has completely supplanted the old sulfuric acid process in the United States, is the direct hydration process. This process, the catalytic vapor-phase hydration of ethylene, is now practiced by only three U.S. companies Union Carbide Corp. (UCC), Quantum Chemical Corp., and Eastman Chemical Co. (a Division of Eastman Kodak Co.). UCC imports cmde industrial ethanol, CIE, from SADAF (the joint venture of SABIC and Pecten [Shell]) in Saudi Arabia, and refines it to industrial grade. 

Indirect Hydration (Esterification—Hydrolysis) Process. The preparation of ethanol from ethylene by the use of sulfuric acid is a three-step process (Fig. 1) ... 

Ethyl Acrylate. The esterification of acryflc acid is a primary use for ethanol. Acryflc acid can also react with either ethylene or ethyl esters of sulfuric acid. 

These processes have supplanted the condensation reaction of ethanol, carbon monoxide, and acetylene as the principal method of generating ethyl acrylate [140-88-5] (333). Acidic catalysts, particularly sulfuric acid (334—338), are generally effective in increasing the rates of the esterification reactions. Care is taken to avoid excessive polymerisation losses of both acryflc acid and the esters, which are accentuated by the presence of strong acid catalysts. A synthesis for acryflc esters from vinyl chloride (339) has also been examined. 

Ethyl Acetate. The esterification of ethanol by acetic acid was studied in detail over a century ago (357), and considerable Hterature exists on deterrninations of the equiUbrium constant for the reaction. The usual catalyst for the production of ethyl acetate [141-78-6] is sulfuric acid, but other catalysts have been used, including cation-exchange resins (358), a- uoronitrites (359), titanium chelates (360), and quinones and their pardy reduced products. 

The vapor-phase esterification of ethanol has also been studied extensively (363,364), but it is not used commercially. The reaction can be catalyzed by siUca gel (365,366), thoria on siUca or alumina (367), zirconium dioxide (368), and by xerogels and aerogels (369). Above 300°C the dehydration of ethanol becomes appreciable. Ethyl acetate can also be produced from acetaldehyde by the Tischenko reaction (370—372) using an aluminum alkoxide catalyst and, with some difficulty, by the boron trifluoride-catalyzed direct esterification of ethylene with organic acids (373). 

An interesting variation of this theme starts with the a-chlorination of dicyclohexylketone (58). Treatment of the halo-genated intermediate with base leads to the acid, 60, by the Favorski rearrangement. Esterification of the acid with 2(1-pyrolidino)ethanol yields dihexyrevine (61). Both this agent and its earlier congener are recommended for use in GI spasms. 

Hydrolysis of the nitrile in 130 (obtained by an alkylation analogous to that used to prepare 126) affords the acid, 131. esterification with ethanol affords the analgesic agent, norpipa-none (132). ... 

The placement of a nitrogen atom directly on the benzilic carbon atom is apparently consistent with antispasmodic activity. Esterification of 2 (iV-piperidyl)ethanol by means of chloroacyl chloride (68) gives the basic ester (69). Displacement of the remaining halogen by piperidine gives dipiproverin (70). ... 

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