Ester under acidic conditions

Tertiary benzylamines react with chloroformate esters under acidic conditions to yield the corresponding benzyl chlorides (equation 173)1096. 

Once the carboxylic acid and the alcohol are formed they are capable of re-reacting so as to re-form the ester. Now consider the situation when the ethyl ester group is substituted by a /-butyl ester group. Write down the equation for the hydrolysis of this new ester under acid conditions. 

The composition of the PAA-g-PS graft copolymer reaction product and its purification, especially as far as the removal of unreacted PS-MA macromonomer by silica column chromatography is concerned, and the successful selective cleavage of the ferf-butyl ester under acidic conditions to render the graft copolyelectrolyte PAA-g-PS were analyzed by XH NMR spectroscopy and SEC. Figure 8a shows the SEC curves of the polystyrene macromonomer (PS-MA), the crude poly (ferf-butyl acrylate-gra/f-styrene) (PTBA-g-PS) and the PTBA-g-PS the polymethylacrylate (PMA) originates from esterification of the poly (acrylic acid) (PAA) obtained after complete saponification of the graft copolymer and represents the backbone. The XH NMR spectra of PSMA, PTBA-g-PS and of the final reaction product PAA-g-PS are shown in Fig. 8b. 

X = Se ". These and other synthesis procedures will be considered in more detail later. Unfortunately, the acetals of (oxomethyl)phosphonic diesters do not liberate the free (oxomethyl)phosphonic esters under acidic conditions, but instead, tend to decompose with the formation of dialkyl hydrogenphosphonate. 

Displayed below is a general mechanism for the Pechmann reaction between a phenol with a m ta-electron-donating group and methyl j -keto ester under acidic conditions. 

Relative reactivities of carboxylic acid derivatives toward nucleophilic acyl substitution. A more reactive derivative may be converted to a less reactive derivative by treatment with an appropriate reagent. Treatment of a carboxylic acid with thionyl chloride converts the carboxylic acid to the more reactive acid chloride. Carboxylic acids are about as reactive as esters under acidic conditions, but are converted to the unreactive carboxylate anions under basic conditions. 

Initially, the product 50 was isolated in 10% yield, but acetyl perchlorate in dichloromethane at -78°C has given a yield of 61% a/p ratio 1.5 1, at the C-1-OAc centre) from tri-O-acetyl-D-glucal 77% of the pure a,a-analogue is obtainable from tri-O-acetyl-D-galactal [25 a]. Not surprisingly, dimers of this kind have been encountered following several reactions of glycal esters under acidic conditions [2]. 

Diterpenes of the labdane or clerodane type continue to stimulate synthetic activity. The butenolide-containing compounds ajugarin-lV " and labda-8(17),-13(14)-dien-15,16-olide have been synthesized.( )-8,9-Dehydroasterolide has been synthesized, using the cyclization of an epoxy-ester under acidic conditions as a key step. 2 ... 

Under acidic conditions, furfuryl alcohol polymerizes to black polymers, which eventually become crosslinked and insoluble in the reaction medium. The reaction can be very violent and extreme care must be taken when furfuryl alcohol is mixed with any strong Lewis acid or Brn nstad acid. Copolymer resins are formed with phenoHc compounds, formaldehyde and/or other aldehydes. In dilute aqueous acid, the predominant reaction is a ring opening hydrolysis to form levulinic acid [123-76-2] (52). In acidic alcohoHc media, levulinic esters are formed. The mechanism for this unusual reaction in which the hydroxymethyl group of furfuryl alcohol is converted to the terminal methyl group of levulinic acid has recendy been elucidated (53). 

Analytical and Test Methods. In addition to the modem spectroscopic methods of detection and identification of pyrroles, there are several chemical tests. The classical Runge test with HCl yields pyrrole red, an amorphous polymer mixture. In addition, all pyrroles with a free a- or P-position or with groups, eg, ester, that can be converted to such pyrroles under acid conditions undergo the Ehrlich reaction with p-(dimethylamino)henzaldehyde to give purple products. 

Another synthesis of the cortisol side chain from a C17-keto-steroid is shown in Figure 20. Treatment of a C3-protected steroid 3,3-ethanedyidimercapto-androst-4-ene-ll,17-dione [112743-82-5] (144) with a tnhaloacetate, 2inc, and a Lewis acid produces (145). Addition of a phenol and potassium carbonate to (145) in refluxing butanone yields the aryl vinyl ether (146). Concomitant reduction of the C20-ester and the Cll-ketone of (146) with lithium aluminum hydride forms (147). Deprotection of the C3-thioketal, followed by treatment of (148) with y /(7-chlotopetben2oic acid, produces epoxide (149). Hydrolysis of (149) under acidic conditions yields cortisol (29) (181). 

Studies of reaction mechanisms ia O-enriched water show the foUowiag cleavage of dialkyl sulfates is primarily at the C—O bond under alkaline and acid conditions, and monoalkyl sulfates cleave at the C—O bond under alkaline conditions and at the S—O bond under acid conditions (45,54). An optically active half ester (j -butyl sulfate [3004-76-0]) hydroly2es at 100°C with iaversion under alkaline conditions and with retention plus some racemization under acid conditions (55). Effects of solvent and substituted stmcture have been studied, with moist dioxane giving marked rate enhancement (44,56,57). Hydrolysis of monophenyl sulfate [4074-56-0] has been similarly examined (58). 

Only in the case of the pyruvic acid condensation product was it possible to isolate the corresponding ethyl ester under these conditions. This, on mild hydrolysis, reverted to 1-methyl-1,2,3,4-tetrahydro-j8-carbohne-1-carboxylic acid, identical with the starting material, which therefore had the assigned structure 26 (R = CH3) and was not the SchiflF s base 25 (R = CH3). Alkaline hydrolysis of the ester was accompanied by decarboxylation. ... 

Ox 0-2,3-dihydro-7//-pyrido[l, 2, i-de]-1,4-benzoxazine-6-carboxylic acids were prepared from 6-esters under acidic (96JAP(K)96/291144, 98MIP19, 98MI37, 99H(51)1563, 99MI36, 00MI76) and under alkalic conditions (OOMIPIO). 

Copper alloys are particularly prone to attack by long-chain fatty acids which are often present in sealing compositions, temporary protectives and as trace additives in many plastics under acid conditions ester plasticisers may saponify in the presence of copper giving rapid corrosion of the copper and accelerating degradation of the polymer. 

Benzothiepins synthesized by a double Knoevenagel condensation (see Section 2.1.1.2.) contain free carboxylic acid groups if the reaction product is isolated under acidic conditions. Rcesterification can be performed by two methods via formation of the acid chloride and subsequent alcoholysis, or by reaction with diazomethane, e.g. the conversion of 3-benzo-thiepin-2,4-diearboxylic acid (5, R = C02H) with thionyl chloride and methanol gives the dimethyl ester 5 (R = C02Me) in 47% yield, while the diazomethane pathway provides 60% of the dimethyl ester.65 Use of excess diazomethane leads to cycloadducts (see Section 2.2.4.). 

The transformation of the porphyrin intermediate 4 into a chlorin can be achieved after introduction of a C — C double bond into the 15-propanoate side chain of 4 to yield 5. The cyclization of 5 with participation of the 15-acrylic ester side chain under acidic conditions gives the chlorin 6 which is then transformed in a multistep reaction sequence into chlorophyll a. The driving force of chlorin formation from the porphyrin is believed to be the relief of steric strain at the sterically overcrowded porphyrin periphery which gives the desired trans arrangement of the propanoate side chain and the methyl group in the reduced ring. The total... 

Alcohol sulfates are half esters of sulfuric acid and contain a C-O-S bond in the molecule. This bond is only relatively stable in water and can hydrolyze, mainly under acidic conditions. The hydrolysis is favored by temperature as was proven in the study of Maurer et al. with octadecyl sulfuric acid [57]. They found that a 0.05 M solution in distilled water at 100°C hydrolyzed to 50% in less than 30 min, whereas at 60°C the hydrolysis was 10% after 3 h and 16% after 7 h. 

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