Esterification organic acids

NaOH solution is added dropwise to an aqueous suspension of this ester at 40—70°C over 1 h and the reaction mixture kept for 2 h to give 86.6% DHNA of 98.7% purity (74), which is then esterified with (CgH O) to obtain PDNA. The esterification process is dramatically improved by adding a small amount of inorganic or organic acid, preferably methanesulfonic acid, benzene sulfonic acid, or naphthalene sulfonic acid subsequent isolation and crystallisation gives a pure product (75). 

Generally, the carboxyl group is not readily reduced. Lithium aluminum hydride is one of the few reagents that can reduce these organic acids to alcohols. The scheme involves the formation of an alkoxide, which is hydroly2ed to the alcohol. Commercially, the alternative to direct reduction involves esterification of the acid followed by the reduction of the ester. 

The butyl alcohols undergo esterification with organic acids in the usual manner in the presence of trace amounts of mineral acid catalysts. Esterification is fastest with /-butyl alcohol and slowest with the primary alcohols although /-butyl alcohol undergoes substantial dehydration in the presence of the typical acid esterification catalysts. 

In the esterification of organic acids with alcohols, it has been shown that in most cases under acid catalysis, the union is between acyl and alkoxy groups. Acid hydrolysis of acetoxysuccinic acid gives malic acid with retention of configuration at the asymmetric carbon atom (11) ... 

Completion of Esterification. Because the esterification of an alcohol and an organic acid involves a reversible equiUbrium, these reactions usually do not go to completion. Conversions approaching 100% can often be achieved by removing one of the products formed, either the ester or the water, provided the esterification reaction is equiUbrium limited and not rate limited. A variety of distillation methods can be appHed to afford ester and water product removal from the esterification reaction (see Distillation). Other methods such as reactive extraction and reverse osmosis can be used to remove the esterification products to maximize the reaction conversion (38). In general, esterifications are divided into three broad classes, depending on the volatility of the esters ... 

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). 

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). 

Because of the insolubility of cellulose it is not possible to carry out uniform esterification with the lower organic acids (acetic acid, propionic acid etc.) and in those cases where incompletely substituted derivatives are required a two-stage reaction is employed. This involves total esterification in a medium in... 

The traditional catalyst used for esterification of acids to methyl esters is sulfuric acid. Homogeneous sulfuric acid catalysis has many downsides. When using sulfuric acid, much capital expense is required for Hastalloy and/or other specialty metals of construction. Homogeneous catalysis results in the contamination of the product by sulfur containing species. Therefore, neutralization and removal of acid is required to meet biodiesel specifications and to protect the downstream transesterification reactor. Inevitably, when using sulfuric acid, organic sulfur compounds will be produced. These products will cause the resultant biodiesel to fail specification tests. 

Esterification Inorganic or organic acids Improved dyeability... 

Neises, B. and W. Steglich, Esterification ofcarboxyic acids with dicyclohexylcarbodiimide/4-dimethylaminopyridine tert-butyl ethyl fumarate. Organic Syntheses, 1990.7 p. 93-94. 

Many petrochemicals have been harnessed because they have two common characteristics they re simple and they re reactive. Acrylic add (AA) is the simplest organic acid that contains a double bond. Its that vinyl group again, CH2=CH-, the same one found in acrylonitrile, styrene, and vinyl chloride. Because it s an acid and because it has the double bond, it s highly reactive. It readily undergoes polymerization (reacts with itself because of the double bond) and esterification (reacts with alcohol because its an acid). 

If you take an alcohol (a compound with an -OH signature) and react it with an organic acid (one with a -COOH signature), the product is an ester (the -COOR signature) and the process is called esterification. If the organic acid you use is acrylic acid, the ester is called an acrylate. And if the alcohol is, say, methyl alcohol, then the product is methyl acrylate, but not methacrylate. If you start out with methacrylic acid, then you get a methacrylate. And finally, if you use methyl alcohol and methacrylic acid, you get methyl methacrylate, which is a big star in petrochemicals. 

Suppose that in an esterification reaction in which an organic acid RCOOH reacts with an alcohol R OH in an organic solvent to produce an ester RCOOR, ... 

Organic esters are formed by the elimination of water between an alcohol and an organic acid (see Esterification). 

Several modifications of the simple direct esterification procedure described above have been developed. For example, it is sometimes convenient to prepare an ester by heating the organic acid, the alcohol and sulphuric acid in a solvent such as toluene. This method is illustrated by the preparation of diethyl adipate for which the procedure is particularly well suited (Expt 5.144). 

Notes. (1) The mother-liquors from the washings and recrystallisations are saved for the recovery of 4-nitrophthalic acid. The combined mother-liquors are concentrated to small bulk and the organic acids extracted into ether. Upon esterification of the residue after evaporation of the ether by the Fischer-Speier method (Section 5.12.3, p. 695), the 3-nitro acid forms the acid ester and may be removed by shaking the product with sodium carbonate solution, while the 4-nitrophthalic acid yields the neutral diester. Hydrolysis of the neutral ester gives the pure 4-nitrophthalic acid, m.p. 165 °C. (2) The acid may also be recrystallised from glacial acetic acid. 

Esterification. Without a doubt, the best known nucleophilic reaction of alcohols is the reaction with organic acids and some derivatives, like acid anhydrides and acid chlorides, to form esters (Reaction XII). 

In general, the acid catalyzed esterification of organic acids can be accomplished easily with primary or secondary alkyl or aryl alcohols, but tertiary alcohols usually give carbonium ions which lead to dehydration. The structure of the acid is also of importance. As a rule, the more hindered the acid is alpha to the carbonyl carbon the more difficult esterification becomes (20A). 

---