Esterification by azeotropic distillation

Enanthaldehyde, -METHYL-/3-OXO-, DIMETHYL ACETAL, 32, 79 Enanthic acid, e-oxo, 31, 3 Epichlorohydrin, 31, 1 Esterification, by azeotropic distillation with toluene, 30, 30, 31 of ethanol with phosphorus trichloride, 31, 111... 

Silica is heated with alcohols containing from two to eighteen carbon atoms to 190° (with primary alcohols) or 275° (with secondary alcohols). For small-chain alcohols an autoclave is used. Esterification with higher-boiling alcohols is achieved simply by refluxing while the water formed in the reaction is removed by azeotropic distillation. A small... 

Dihexylxylaramide (2). To a 250 mL round-bottom flask equipped with a magnetic stirrer was added methanol (150 mL), and the flask then cooled to 5 C. Acetyl chloride (5 mL) was added to the cold methanol and then xylaric acid (18 g, 0.18 mol, reference 18) was added to the methanolic HCl solution. The reaction mixture was refluxed for 16 h, concentrated to a syrup, and residual water removed from the syrup by azeotropic distillation with benzene. Esterification was complete but the product (1) contained more than one ester component as both ester and 5-membered lactone functions were observed in its IR spectrum (neat, 1745 and 1795 cm, ester and lactone C=0 respectively). 

This reaction, known as Fischer esterification, requires the presence of an acid catalyst. Because the carboxylic acid and the ester have similar reactivities, the reaction is useful only if a method can be found to drive the equilibrium in the direction of the desired product—the ester. In accord with Le Chatelier s principle, this is accomplished by using an excess of one of the reactants or by removing one of the products. An excess of the alcohol is used if it is readily available, as is the case for methanol or ethanol. Or water can be removed by azeotropic distillation with a solvent such as toluene. 

Esterification—Continued by azeotropic distillation with benzene, 22, 38 by nitric acid, 22, 65 of desoxycholic acid, 24, 41 of lactic acid, 26, 4 of linoleic acid, 22, 77 of linolenic acid, 22, 83 of pyruvic acid with use of methyl ester column, 24, 72 Ester interchange, 26, 5, 19 between polylactic acid and allyl alcohol, 26, 5... 

Esterification is usually effected by refluxing the acid and alcohol with a small amount of sulfuric acid, hydrogen chloride, or arylsulfonic acid. The equilibrium is shifted to the right by an excess of one of the reactants or by removal of water either by azeotropic distillation or by means of a suitable drying agent. The necessity for continuous drying is eliminated when methylene or ethylene chlorides are used as solvents for the reaction. A small amount of an acid chloride such as thionyl chloride, acetyl chloride, or stearoyl chloride has proved superior to hydrogen chloride as a catalyst for certain esterifications at room temperature. ... 

Substituted oxazolidin-5-one derivatives, which are prepared from N -protected a-annino dicarboxyhc acids and paraformaldehyde, are employed for dual protection of the a-annino and a-carboxy groups in the synthesis of P-aspartyl and y-glutamyl esters (Scheme 4).Py For this purpose the oxazolidinone derivatives are synthesized by treatment of the Z amino acids with paraformaldehyde in a nnixture of acetic anhydride, acetic acid, and traces of thionyl chloride or by azeotropic distillation of the Z amino acids with paraformaldehyde and 4-toluenesulfonic acid in benzene. The resulting heterocychc compounds are readily converted into the tert-butyl esters with isobutene under acid catalysis. Esterification is achieved with tert-butyl bromidet or with Boc-F.P l Finally, the oxazolidinone ring is opened by alkaline hydrolysis or catalytic hydrogenolysis to yield the tert-butyl esters. 

All these distillations are conducted in the presence of a polymerization inhibitor (200 ppm of hydroquinone or its monoethyl ether), introduced at the irifiix level, and in moderate bottom temperature conditions (100 to 110°C maximum), and hence under reduced pressure if necessary. The different aqueous phases, especially the water extract of the alcohol, are stripped to recover tbe ternary acrylate/alcohol/watcr azeotrope at the top, which is recycled to the extraction step (case of butanol in particular), and a water/alcohol mixture at the bottom, which may be separated by azeotropic distillation. The molar yield of esterification is 90 to 95 per cent in relation to acryfic arid. 

The batch synthesis data [Geladi Forsstrom 2002] is concerned with the production of isoamyl acetate by an esterification from isoamyl alcohol and acetic acid in a boiling reaction mixture. An acid catalyst is needed and paratoluenesulphonic acid is used. Water is removed by azeotropic distillation with benzene for moving the equilibrium towards the... 

Although the previous two sections of this chapter emphasized hydrolytic processes, two mechanism that led to O or N-acylation were considered. In the discussion of acid-catalyzed ester hydrolysis, it was pointed out that this reaction is reversible (p. 654). Thus it is possible to acylate alcohols by acid-catalyzed reaction with a carboxylic acid. This is called the Fischer esterification method. To drive the reaction forward, the alcohol is usually used in large excess, and it may also be necessary to remove water as it is formed. This can be done by azeotropic distillation in some cases. 

Continuous removal of the product water by azeotropic distillation after addition of a carrier such as benzene, toluene, xylene, or a halogenated aliphatic solvent leads to rapid esterification ( azeotropic esterification ) and usually also to high yields. The course of the reaction can be followed directly from the amount of water liberated the apparatus used for this purpose (a water separator) is well known. 

Reaction of 1-pentanol with propionic acid provides 1-pentyl propionate [624-54-4] a new coatings solvent for automotive refinish and OEM paints, appHances, and for higher-soHds systems (37). The esterification of 1-pentanol with formic acid to 1-pentyl formate [638-49-3] is conducted by concomitant removal of by-product water by azeotropic distillation with diethyl ether (38). 

An example of a typical batch preparation of a polyester is one where 1.2 moles of propylene glycol, 0.67 mole of maleic anhydride, and 0.33 mole of phthalic anhydride are combined. Propylene glycol is used in excess to compensate for loss during the reaction. The condensation at 150-200 °C lasts for 6-16 hours, with constant removal of water, the byproduct. An aromatic solvent, like toluene or xylene, is often added to the reaction mixtures to facilitate water removal by azeotropic distillation. Esterification catalysts, like toluene sulfonic acid, reduce the reaction time. In addition. 

There are two main methods for preparation of alkyd resins. In the first one, called the fatty acid process, a free fatty acid is coesterified directly with the dibasic acid and the polyol at 200-240 °C. The reaction may be carried out without a solvent by first heating in an inert atmosphere. At the end, an inert gas may be blown into the resin from the bottom of the reaction kettle to remove water and unreacted materials. As a modification of this, a small quantity of a solvent may be used to remove water of esterification continuously by azeotropic distillation with the aid of moisture traps. 

Vegetable oil-based poly(ester amide)s are prepared by a three-step reaction procedure in which a base such as sodium methoxide is used as the catalyst for the first two steps and metal oxide/hydroxide is used for the last step of the reaction (Fig. 5.2). In the first step, methyl esters of the fatty acids are produced by transesterifiction of oil with methanol, followed by transformation to dihydroxy fatty amide by amidation reaction with dihydroxyalkylamine and, finally, esterification reaction by treatment with dibasic acid or anhydride at a relatively high temperature to obtain the desired poly (ester amide). This may be done either by azeotropic distillation or by direct polycondensation under an inert atmosphere. Poly(ester amide) can also be synthesised at a low temperature through a condensation polymerisation reaction in the absence of an organic solvent. In this reaction, V,V-bis(2-hydroxyalkyl) fatty amide and dibasic anhydride are heated at a temperature lower than the onset of the melting points of the component. By-products, such as water, are removed by a vacuum technique. 

Some indication of at least the maximum size of the silicate species in a solution of sodium silicate of 3.3 ratio SiOjrNajO has been obtained from the nature of the corresponding silicic acid ester (69). Silicic acid of low molecular weight is so unstable in aqueous solutions that any attempt to isolate it by evaporation of water, even at ordinary temperature, results in rapid polymerization to a gel. The direct esterification of silicic acid therefore remained impractical until the discovery of Kirk (70) of a method for transferring silicic acid of low molecular weight from aqueous solution to solution in an alcohol. This transfer is accomplished by extraction of the acid with a suitable polar organic solvent, simultaneously saturating the aqueous phase with sodium chloride in order to salt the silicic acid into the organic phase. An alcohol such as rt-butyl alcohol is then added, and esterification is effected by azeotropic distillation of water from the alcohol solution (29). 

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