Esters alcohol interchange

Prepared generally by ester interchange from polyvinylacelate (ethanoate) using methanol and base also formed by hydrolysis of the acetate by NaOH and water. The properties of the poly(vinyl alcohol) depend upon the structure of the original polyvinyl acetate. Forms copolymers. Used as a size in the textile industry, in aqueous adhesives, in the production of polyvinyl acetates (e.g. butynal) for safety glasses. U.S. production 1980... 

Dinitrobenzoates. The 3,5-dinitrobenzoate of the alcohol portion of the ester may be obtained by ester interchange. Thus an ester, R -COOR, when heated with 3,5 dinitrobenzoic acid and sulphuric acid gives (N03)2CgH3C00R. 

AH the common monobasic (107) and dibasic esters (108) of tetrahydrofurfuryl alcohol have been prepared by conventional techniques the dibasic esters and some of the mono esters are effective as primary or secondary plasticizers for vinyl polymers. Tetrahydrofurfuryl acrylate [2399-48-6] and methacrjiate [2455-24-5] specialty monomers, have been produced by carbonylation (nickel carbonyl and acetylene) of the alcohol (109) as weU as by direct esterification (110—112) and ester interchange (111). 

The addition of alcohols to form the 3-alkoxypropionates is readily carried out with strongly basic catalyst (25). If the alcohol groups are different, ester interchange gives a mixture of products. Anionic polymerization to oligomeric acrylate esters can be obtained with appropriate control of reaction conditions. The 3-aIkoxypropionates can be cleaved in the presence of acid catalysts to generate acrylates (26). Development of transition-metal catalysts for carbonylation of olefins provides routes to both 3-aIkoxypropionates and 3-acryl-oxypropionates (27,28). Hence these are potential intermediates to acrylates from ethylene and carbon monoxide. 

Patty esters (wax esters), formed by ester interchange of the product alcohol and the starting material in the hydrogenolysis reactors, are later separated from the product by distillation. Unreacted methyl esters are also converted to fatty esters in the distillation step... 

RandomiZation/Interesterification. Transesterification occurs when a carboxyUc acid (acidolysis) or alcohol (alcoholysis) reacts with an ester to produce a different ester (20). Ester—ester interchange is also a form of transesterification. If completely unsaturated triglyceride oil (UUU) reacts with a totally saturated fat (SSS) in the presence of an active catalyst such as sodium, potassium, or sodium alkoxide, triglycerides of intermediate composition may be formed. 

Mixed esters can be prepared from Cl Ti(OR)4 and a second alcohol in the presence of a base or by mixing a tetraalkoxide and the second alcohol in the desired proportions and flash-evaporating the mixed alcohols. Mixing of two pure tetraalkoxides of titanium also leads, via a rapid ester interchange reaction, to a mixture of ah. possible combinations of tetraalkyl titanates. 

Esters are most commonly prepared by the reaction of a carboxyHc acid and an alcohol with the elimination of water. Esters are also formed by a number of other reactions utilizing acid anhydrides, acid chlorides, amides, nitriles, unsaturated hydrocarbons, ethers, aldehydes, ketones, alcohols, and esters (via ester interchange). Detailed reviews of esterification are given in References 1—9. 

It is essential to neutralize any strong acid present before distilling lactic esters otherwise, condensation by ester interchange occurs, with liberation of alcohol and production of polylactic acid, a linear polyester. Other neutralizing agents, such as alkali or alkaline-earth hydroxides or carbonates, doubtless could be used satisfactorily instead of sodium acetate. 

Esters react with alcohols in either aeidic or basic solution to exchange alkoxy groups (ester interchange) by mechanisms which parallel hydrolysis. The alcohol or alkoxide acts as the nucleophile ... 

The triester of ethylene chlorohydrin readily undergoes ester interchange with higher alcohols, e.g., 2-ethylhexanol. The formed ethylene chlorohydrin is distilled off. The reaction is applicable to all alcohols having a higher boiling point than ethylene chlorohydrin. 

As a practical matter, the alkoxide used as the base must be the same as the alcohol portion of the ester to prevent product mixtures resulting from ester interchange. Sodium hydride with a small amount of alcohol is frequently used as the base for ester condensation. The reactive base is the sodium alkoxide formed by reaction of sodium hydride with the alcohol released in the condensation. 

Estane, commercial block copolymer, 7 648t Ester—acid interchange, 10 492-493 Ester—alcohol interchange, 10 491—492 Esterases, 3 675-676 Ester bonds, in the wood cell wall, 21 15 Ester carboxylates, 24 144, 145 Ester-ester interchange, 10 493 Ester hydrolysis, 10 497, 502—503 Esterifiable acids, 10 490 Esterification, 9 283, 320 10 471-496. 

To get to the end product, the higher dcohol, the triglycerides go through a two-step process. First, the branches are split from the triglyceride in an ester interchange by reacting with methanol. Other alcohols are sometimes used but the methanol turns up again later in the process and is relatively easy to separate from the other reactants. 

The final step drives the reaction to completion. Ethyl acetoacetate is more acidic than any of the other species present, and it is converted to its conjugate base in the final step. A full equivalent of base is needed to bring the reaction to completion. The /i-kctocstcr product is obtained after neutralization and workup. As a practical matter, the alkoxide used as the base must be the same as the alcohol portion of the ester to prevent product mixtures resulting from ester interchange. Because the final proton transfer cannot occur when a-substituted esters are used, such compounds do not condense under the normal reaction conditions. This limitation can be overcome by use of a very strong base that converts the reactant ester completely to its enolate. Entry 2 of Scheme 2.13 illustrates the use of triphenylmethylsodium for this purpose. 

Transesterification. When esters are heated with alcohols, acids, or other esters in (he presence of a catalyst, the alcohol or acid groups are exchanged. This process is called transesterificaiion. It is accelerated by the presence of a small amount of acid or alkali. Three types of transesterilication are known (/) exchange of alcohol groups (alcoholysis). (2 i exchange of acid groups (acidolysis). and (3) ester-ester interchange. Sec also Esterification. 

Ester interchange is closely related to ester hydrolysis. This is a base-catalyzed reaction that is useful to replace the alcohol group of an ester with a different alcohol group. The catalyst is alkoxide ion and the equilibrium constant is close to unity, unless the alcohols differ greatly in size. An example is... 

Ester interchange H or OH RC02R + R OH < =t RC02R" + R OH Acid- and base-catalyzed generally limited to primary alcohols (for discussion, see Section 18-7A). 

This mechanism adequately coordinates the well-known variations of base-induced dismutations of aldehydes into a general picture and makes it unnecessary to suppose that different bases act in different ways. The formation of esters when an aldehyde is treated with an alkoxide follows the same scheme, with OR- in place of OH-, and takes into account the ester interchanges which have been observed to occur. The transformation of benzaldehyde into benzamide and benzyl alcohol by the action of sodamide 18 proceeds analogously, amide-ester interchange brought about by the amide ion being the last step. 

Ester interchange,3 Exchange of methyl or ethyl esters can be conducted with 1 equiv. of an alcohol and a base (K2CO,) in the presence of Aliquat or Bu4NHS04 and in the absence of an additional solvent. Indeed it can be carried out at 70° in the absence of a phase-transfer catalyst. 

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