Esters Formates

The preparation of -butyl bromide as an example of ester formation by Method 1 (p. 95) has certain advantages over the above preparation of ethyl bromide. -Butanol is free from Excise restrictions, and the -butyl bromide is of course less volatile. and therefore more readily manipulated without loss than ethyl bromide furthermore, the n-butyl bromide boils ca. 40° below -butyl ether, and traces of the latter formed in the reaction can therefore be readily eliminated by fractional distillation. 

Ester formation. Heat gently i ml. of ethanol with 0 5 g. of the acid or one of its salts and a few drops of cone. HjSO for about I minute. Cool and pour into a few ml. of water in a test-tube and note the odour. The test is particularly useful for identifying ... 

Ester formation. Add carefully 1 ml. of the liquid to i ml. of ethanol and then warm gently for i minute. Pour into water, make alkaline with aqueous Na2C03 solution (to remove HCl and other acid fumes), and note the odour of ethyl acetate or ethyl benzoate. 

Ester formation. Heat under very efficient reflux 1 ml. of diethyl ether, 4 ml. of glacial acetic acid and i ml. of cone. H2SO4 for ro minutes. Distil off 2 ml. of liquid. Use a few drops of this liquid for the hydroxamic add test for esters (p. 334). Use the remainder for other tests for esters (p. 354). 

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]. ... 

When esterification is the objective water is removed from the reaction mixture to encourage ester formation When ester hydrolysis is the objective the reaction is carried out m the presence of a generous excess of water Both reactions illustrate the applica tion of Le Chatelier s principle (Section 6 10) to organic synthesis... 

The mechanism of acid catalyzed ester hydrolysis is presented m Figure 20 4 It IS precisely the reverse of the mechanism given for acid catalyzed ester formation m Section 19 14 Like other nucleophilic acyl substitutions it proceeds m two stages A... 

Polyesters are a second class of condensation polymers and the principles behind their synthesis parallel those of polyamides Ester formation between the functional groups of a dicarboxylic acid and a diol... 

Ester formation is a typical reaction of the carboxyl group... 

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... 

Earlier reports have indicated that esters can form before significant amounts of acids accumulate (16). The Bayer-ViUiger oxidations of ketones with intermediate hydroperoxides and/or peracids have been suggested as ester forming mechanisms (34,56). However, the reactions of simple aUphatic ketones with peracetic acid are probably too slow to support this mechanism (57,58). Very early proposals for ester formation, although imaginative, appear improbable (59). 

Genetic manipulation or cloning offers many possibiUties and perhaps there will be yeast strains especially designed for special beers, ie, types, which are usehil because of low diacetyl formation, high—low ester formation, and insensitivity to pressure or high fermentation temperatures or extracellular enzymatic abiUties (P-glucanases). 

Hypochlorous acid undergoes a variety of reactions with organic substances including addition, oxidation, C- and iV-chlorination, and ester formation. On an industrial scale, hypochlorous acid, generated m situ via chlorine hydrolysis, reacts with propylene forming primarily the a-propjlene chlorohydrin isomer. 

The mechanisms of oxidation using bismuthate, periodate or lead tetraacetate, while still not completely understood, are probably similar, involving some type of cyclic ester formation as the first step. ... 

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

Note that the reverse reaction is acid-catalyzed ester formation.) The rate equation is... 

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. ... 

SOME GENERAL METHODS FOR PHOSPHATE ESTER FORMATION REMOVAL OF PROTECTIVE GROUPS FROM PHOSPHORUS... 

Cleavage is achieved with refluxing NaOH (15 min), but some deamination occurs with deoxyriboadenosine-5 -phosphate. The ester is formed using the DCC protocol for phosphate ester formation. 

Anhydrides and esters may differ in two ways. One may undergo nucleophilic addition more rapidly (kinetics), but the other may create a more favorable equilibrium constant for ester formation (thermodynamics). 

Benzoyl chloride reacts with 2-mercaptoethanol in base to give an ester. When the reaction is monitored carefully, the rapid buildup of an intermediate, X , of molecular formula C9H10O2S, is observed. This is slowly transformed into the ester of the same molecular formula. Although ester formation is known to be a multi-step process, X does not correspond to any of the usual intermediates in ester formation. What is going on here ... 

More importantly, Peet and coworkers reported the reaction of o-nitroaniline 35 with acetylene dicarboxylate 32 to provide fumarate 36. Subsequent cyclization proved difficult under thermal conditions and only a 35% yield of quinolone 37 was isolated. Use of PPA for the cyclization improved the yield of 37 significantly. Using this modification allowed enamino-ester formation with a nitro-group attached to the arylamine. 

Despite several attractive features in this method of direct halogen introduction and the obvious applications in the synthesis of deoxy sugars, its uses have not been further exploited by other groups of workers. Some new related methods have become available which reportedly eliminate the difficulties previously encountered such as rearrangement, unreactivity due to steric hindrance, and phosphonate ester formation. The reaction is based on the observation (28) that triethylphosphine reacts with ethanol and carbon tetrachloride to give ethyl chloride, chloroform, and triethylphosphite. In a new adaptation (76, 77) of this... 

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. 

An important reaction of fats is the reverse of ester formation. They hydrolyze, or react with water, just as disaccharides do. Usually hydrolysis is carried out in aqueous Ca(OH)2, NaOH, or KOH solution. Because of long use in the preparation of soap from fats, the alkaline hydrolysis reaction (6) is called saponification. 

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