Alcohols ester formation

Under CO pressure in alcohol, the reaction of alkenes and CCI4 proceeds to give branched esters. No carbonylation of CCI4 itself to give triichloroacetate under similar conditions is observed. The ester formation is e.xplained by a free radical mechanism. The carbonylation of l-octene and CCI4 in ethanol affords ethyl 2-(2,2,2-trichloroethyl)decanoate (924) as a main product and the simple addition product 925(774]. ... 

Fingerprint region (Section 13 20) The region 1400-625 cm of an infrared spectrum This region is less character istic of functional groups than others but varies so much from one molecule to another that it can be used to deter mine whether two substances are identical or not Fischer esterification (Sections 15 8 and 19 14) Acid cat alyzed ester formation between an alcohol and a carboxylic acid... 

Esters of medium volatility are capable of removing the water formed by distillation. Examples are propyl, butyl, and amyl formates, ethyl, propyl, butyl, and amyl acetates, and the methyl and ethyl esters of propionic, butyric, and valeric acids. In some cases, ternary azeotropic mixtures of alcohol, ester, and water are formed. This group is capable of further subdivision with ethyl acetate, all of the ester is removed as a vapor mixture with alcohol and part of the water, while the balance of the water accumulates in the system. With butyl acetate, on the other hand, all of the water formed is removed overhead with part of the ester and alcohol, and the balance of the ester accumulates as a high boiler in the system. 

Fischer esterification (Sections 15.8 and 19.14) Acid-catalyzed ester formation between an alcohol and a carboxylic acid ... 

The Dmab group was developed for glutamic acid protection during Fmoc/r-Bu based peptide synthesis. The group shows excellent acid stability and stability toward 20% piperidine in DMF. It is formed from the alcohol using the DCC protocol for ester formation and is cleaved with 2% hydrazine in DMF at rt. ... 

The required nitro compounds are easy to prepare, and are useful building blocks for synthesis. Treatment with an appropriate base—e.g. aqueous alkali—leads to formation of nitronates 2. Various substituted nitro compounds, such as nitro-ketones, -alcohols, -esters and -nitriles are suitable starting materials. 

The net effect of Fischer esterification is substitution of an -OH group by —OR. Aii steps are reversible, and the reaction can be driven in either direction by choice of reaction conditions. Ester formation is favored when a large excess of alcohol is used as solvent, but carboxylic acid formation is favored when a large excess of water is present. 

Strategy The Claisen condensation of an ester results in loss of one molecule of alcohol and formation of a product in which an acyl group of one reactant bonds to the a carbon of the second reactant. The product is a /3-keto ester. 

Ester formation is an example of a condensation reaction in which two molecules combine to form a larger one and a small molecule is eliminated (Fig. 19.4). The reaction is catalyzed by a small amount of strong acid, such as sulfuric acid. In an esterification of a carboxylic acid and an alcohol, the eliminated molecule is H20. 

Trifluoromethanesulfonates of alkyl and allylic alcohols can be prepared by reaction with trifluoromethanesulfonic anhydride in halogenated solvents in the presence of pyridine.3 Since the preparation of sulfonate esters does not disturb the C—O bond, problems of rearrangement or racemization do not arise in the ester formation step. However, sensitive sulfonate esters, such as allylic systems, may be subject to reversible ionization reactions, so appropriate precautions must be taken to ensure structural and stereochemical integrity. Tertiary alkyl sulfonates are neither as easily prepared nor as stable as those from primary and secondary alcohols. Under the standard preparative conditions, tertiary alcohols are likely to be converted to the corresponding alkene. 

Other Gas Reactions. Several other reactive gases or vapours were examined but found to be unsatisfactory. No ester formation ( 1745 cm"1) was found when oxidatized films were exposed to acetic acid or formic acid vapour. Alcohol/carboxylic acid reactions in the solid state have often been suggested as the source of ester products, but not substantiated (4,5). Gaseous ammonia reacted with carboxylic acid groups to give absorptions at 1550 cm"1 [-C(=0)-0 ] and 1300 cm"1 (NHi +). However, these absorptions were very broad and the method inferior to acid measurement by SF. Although N20 did not react with oxidized polyolefins, the reaction of N02 with oxi-... 

Ester formation from polysaccharides can be achieved in several ways First by acylation of the OH groups with carboxylic or sulfonic acid azolides, second by converting the OH groups with imidazole carboxylates into carbonates, and third by reaction of an acid leash on the polysaccharide with an alcohol by means of CDI or analogous azolides. The acid leash might, for example, be a succinate attached to the polysaccharide. 

Production of acetate ester pheromone components utilizes an enzyme called acetyl-CoA fatty alcohol acetyltransferase that converts a fatty alcohol to an acetate ester. Therefore, alcohols could be utilized as substrates for both aldehyde and acetate ester formation. In some tortricids an in vitro enzyme assay was utilized to demonstrate specificity of the acetyltransferase for the Z isomer of ll-14 OH [66]. This specificity contributes to the final ratio of... 

H. Ito, T. Tada, M. Sudo, Y. Ishida, T. Hino, and K. Saigo, [60]Fullerenoacetyl chloride as a versatile precursor for fullerene derivatives Efficient ester formation with various alcohols, Org. Lett., 5 (2003) 2643-2645. 

Ester formation by dimethylsulfate or diazomethane is not satisfactory because the microgels become insoluble when the reaction proceeds to higher conversions. With diazomethane part of the unsaturated groups is involved in a side reaction of a 1,3-dipolar cycloaddition [132]. A more efficient method for ester formation of microgels is the reaction with 0-alkyl-N,N -bisisopropyl isoureas of the alcohols. The alkyl ureas are easily separated from solutions in methanol [294-296]. The esterified microgels were isolated by precipitation and freeze-drying. Depending on the alcohol used for ester formation, the yields of... 

In the original paper, the authors performed the reaction using commercially available bakers yeast from a supermarket or bakery. Initially a trial run using similar quantities of Sigma dried yeast resulted in an extremely vigorous initial fermentation, so the quantity of dry yeast was reduced by factor of 5. The contributors assessed the enantiomeric excess of the alcohol by formation of the (+)-MTPA ester and examination of the 19F NMR spectrum. However, the value obtained for the optical rotation was consistent with that reported in the literature. 

VI. Reaction of Aldonolactones with Alcohols 1. Formation of Esters... 

Figure 12.13. Ester formation by direct attack of alcohol...

The last possibility for ester formation (20, Figure 12.15) comprises the reductive elimination of esters from acyl-alkoxy-palladium complexes 17, formed by deprotonation of the alcohol adducts 16. Clearly, it requires cis coordination of the alkoxide and acyl fragment. Since monodentates have a preference for ester formation, it was thought that this mechanism was very unlikely. 

One fact to keep in mind with such phases is that weak acid cation-exchange materials based on carboxylic acid functional groups are subject to esterification in the presence of alcohol containing eluents. Even thongh typical eluent conditions (i.e., weakly acidic aqneous eluents containing alcohol) do not favor ester formation, such stationary phases typically exhibit slowly declining capacity when operated in the presence of alcohol-containing eluents. Consequently, such columns are normally operated with acetonitrile, tetrahydrofuran or acetone rather than with methanol, in order to avoid this problem. 

Complex 77 has also been reported to catalyze the oxidative dimerization of alcohols to esters when the reactions are performed in the presence of base [76]. The presence of base presumably encourages the reversible attack of the alcohol onto the initially formed aldehyde to give a hemiacetal, which is further oxidized to give the ester product. Alcohols 87 and 15 were converted into esters 88 and 89 with good isolated yields (Scheme 20). Alternative iridium catalysts have been used for related oxidative dimerization reactions, and the addition of base is not always a requirement for the reaction to favor ester formation over aldehyde formation [77, 78]. 

The influence of temperature on the ortho effect has been evaluated in the alkaline hydrolysis in aqueous DMSO solutions of ortho-, meta- and para-substituted phenyl benzoates (26). The alcoholysis of phthalic anhydride (27) to monoalkyl phthalates (28) occurs through an A-2 mechanism via rate-determining attack of the alcohol on a carbonyl carbon of the anhydride (Scheme 4). Evidence adduced for this proposal included highly negative A 5 values and a p value of 4-2.1. In the same study, titanium tetra-n-butoxide and tri-n-butyltin ethanoxide were shown to act as effective catalysts of the half-ester formation from (27), the mechanism involving alkoxy ligand exchange at the metal as an initial step. ... 

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