Hydrolysis of methylated

Hydrolysis of methyl oxalate. The exceptionally rapid hydrolysis of rnethyl oxalate can be followed thus Dissolve 0 2 g. of finely powdered methyl oxalate in 10 ml. of water, and add i drop of phenolphthalein. Then add very dil. NaOH solution (1%) drop by drop until the solution just turns pink it will be noticed that the colour rapidly fades, but is restored on the Further addition of 1-2 drops of NaOH solution. The colour fades again and the addition can be repeated until hydrolysis is complete. Oxalic acid (with which methyl oxalate may be confused) gives a precise end-point when treated with NaOH solution in this way. 

Hydrolysis of methyl m-nitrobenzoate to m-nitrobenzoic acid. Place 90 -5 g. of methyl m-nitrobenzoate and a solution of 40 g. of sodium hydroxide in 160 ml. of water in a 1-htre round-bottomed flask equipped with a reflux condenser. Heat the mixture to boiling during 5-10 minutes or until the ester has disappeared. Dilute the reaction mixture with an equal volume of water. When cold pour the diluted reaction product, with vigorous stirring, into 125 ml. of concentrated hydrochloric acid. Allow to cool to room temperature, filter the crude acid at the pump and wash it with a httle water. Upon drying at 100°, the crude m-nitrobenzoic acid, which has a pale brownish colour, weighs 80 g. and melts at 140°, Recrystalhsation from 1 per cent, hydrochloric acid afibrds the pure acid, m.p. 141°, as a pale cream sohd the loss of material is about 5 per cent. 

A new approach we found is based on the initial bromination of methane to methyl bromide, which can be effected with good selectivity, although still in relatively low yields. Methyl bromide is easily separated from exeess methane, whieh is readily recyeled. Hydrolysis of methyl bromide to methyl alcohol and its dehydration to dimethyl ether are readily achieved. Importantly, HBr formed as by produet ean be oxidatively reeycled into bromine, making the overall proeess cat-alytie in bromine. 

Is the two step sequence depicted in the following equations con sistent with the second order kinetic behavior observed for the hydrolysis of methyl bromide ... 

Poly(acrylic acid) and Poly(methacrylic acid). Poly(acryHc acid) (8) (PAA) may be prepared by polymerization of the monomer with conventional free-radical initiators using the monomer either undiluted (36) (with cross-linker for superadsorber appHcations) or in aqueous solution. Photochemical polymerization (sensitized by benzoin) of methyl acrylate in ethanol solution at —78° C provides a syndiotactic form (37) that can be hydrolyzed to syndiotactic PAA. From academic studies, alkaline hydrolysis of the methyl ester requires a lower time than acid hydrolysis of the polymeric ester, and can lead to oxidative degradation of the polymer (38). Po1y(meth acrylic acid) (PMAA) (9) is prepared only by the direct polymerization of the acid monomer it is not readily obtained by the hydrolysis of methyl methacrylate. 

Coproductioa of ammonium sulfate is a disadvantage of the formamide route, and it has largely been supplanted by processes based on the direct hydrolysis of methyl formate. If the methanol is recycled to the carbonylation step the stoichiometry corresponds to the production of formic acid by hydration of carbon monoxide, a reaction which is too thermodynamicaHy unfavorable to be carried out directly on an iadustrial scale. 

Thermal chlorination of methane was first put on an industrial scale by Hoechst in Germany in 1923. At that time, high pressure methanol synthesis from hydrogen and carbon monoxide provided a new source of methanol for production of methyl chloride by reaction with hydrogen chloride. Prior to 1914 attempts were made to estabHsh an industrial process for methanol by hydrolysis of methyl chloride obtained by chlorinating methane. 

Ion exchange resin heads used as column packing Hydrolysis of methyl acetate t lichigami, J. Chem. Eng. Jap., 23,. 354 (1990)... 

Slotted plate for catalyst support designed with openings for vapor flow Ion exchanger fibers (reinforced ion exchange polymer) used as solid-acid catalyst None specified Hydrolysis of methyl acetate Evans and Stark, Eiir. Pat. Appl. EP 571,163 (1993) Hirata et al., Jap. Patent 05,212,290 (1993)... 

An instance of autocatalysis is the hydrolysis of methyl acetate, which is catalyzed by product acetic acid, A C. The rate equation may be... 

The TCBOC group is stable to the alkaline hydrolysis of methyl esters and to the acidic hydrolysis of r-butyl esters. It is rapidly cleaved by the supemucleophile lithium cobalt(I)phthalocyanine, by zinc in acetic acid, and by cobalt phthalocy-anine (0.1 eq., NaBH4, EtOH, 77-90% yield). 

While it may be convenient to use optically active reactants to probe the stereochemistry of substitution reactions, it should be emphasized that the stereochemistry of a reaction is a feature of the mechanism, not the means of determining it. Thus, it is proper to speak of a substitution process such as the hydrolysis of methyl iodide as proceeding... 

Inversion of configuration at carbon in hydrolysis of methyl iodide. 

The hydrolysis of methyl aeetate is an autoeatalytie reaetion and is first order with respeet to both methyl aeetate and aeetie aeid. The reaetion is elementary, bimoleeular and ean be eonsidered iiTeversible at eonstant volume for design purposes. The following data are given ... 

Thus curvature in an Arrhenius plot is sometimes ascribed to a nonzero value of ACp, the heat capacity of activation. As can be imagined, the experimental problem is very difficult, requiring rate constant measurements of high accuracy and precision. Figure 6-2 shows a curved Arrhenius plot for the neutral hydrolysis of methyl trifluoroacetate in aqueous dimethysulfoxide. The rate constants were measured by conductometry, their relative standard deviations being 0.014 to 0.076%. The value of ACp was estimated to be about — 200 J mol K, with an uncertainty of less than 10 J moE K. ... 

Figure 6-2. Curved Arrhenius plot for the hydrolysis of methyl trifluoroacetate in dimethylsulfoxide-water (mole fraction water = 0.973). ...

These rate constants are for the basic hydrolysis of methyl 4-substituted 2,6-dimethylbenzoates at 125°C in 60% dioxane. 

In a penicillin synthesis, the carboxyl group was protected as a / -bromophenacyl ester that was cleaved by nucleophilic displacement (PhSK, DMF, 20°, 30 min, 64% yield). Hydrogenolysis of a benzyl ester was difficult (perhaps because of catalyst poisoning by sulfur) basic hydrolysis of methyl or ethyl esters led to attack at the /3-lactam ring. ... 

The aforementioned exception and the rather limited experimental material available do not allow any conclusions about the general applicability of the Hammett equation, using the same a- and p-values as for benzenes, to be drawn with certainty. The present author has pointed out that large deviations should be expected with strong - -M-substituents, as is also indicated from the rates of alkaline hydrolysis of methyl 5-amino- and 5-acylamino-2-thenoates. From the chemical shifts in the NMR spectra of thiophenes and benzenes it appears that another set of cr-values should be used in the thiophenes series which seems plausible since the transmission of the sub-... 

The chloro atom of 2-[4-(6-chloronicotinoyl)benzyloxy]-3-methyl-4//-pyrido[l,2-n]pyrimidin-4-one, its 6-methyl derivative and 2-[4-(6-chlo-ronicotinoyl)benzylthio]-3-methyl-4//-pyrido[l,2-n]pyrimidin-4-one was replaced by a 4-piperidinopiperidino and 4-phenylpiperazino group with 4-piperidinopiperidine and 4-phenylpiperazine (96EUP733633). The carboxyl group of 2-[4-(4-carboxybenzoyl)benzyloxy]-3-methyl-4//-pyrido[l,2-n]pyrimidin-4-one, prepared by hydrolysis of methyl ester in DMF with 1 N NaOH, was reacted first with diethyl pyrocarbonate in DMF at room temperature and then with 4-phenylpiperazine and 4-piperidinopiperidine to give the appropriate amide derivatives (96EUP733633). 

A reaction with a rate constant that conforms to Eq. (10-21)—particularly to the feature that the catalysts are H+ and OH-, and not weak acids and bases—is said to show specific acid-base catalysis. This phenomenon is illustrated by the kinetic data for the hydrolysis of methyl o-carboxyphenyl acetate16 (the methyl ester of aspirin— compare with Section 6.6) ... 

The pH profile for the hydrolysis of methyl aspirin, which shows specific acid-base catalysis. The solid line shows the fit according to Eq. (10-21), and the dashed one where ko = 0. Data are from Ref. 16. 

The intermediates 74 and 76 can now lose OR to give the acid (not shown in the equations given), or they can lose OH to regenerate the carboxylic ester. If 74 goes back to ester, the ester will still be labeled, but if 76 reverts to ester, the 0 will be lost. A test of the two possible mechanisms is to stop the reaction before completion and to analyze the recovered ester for 0. This is just what was done by Bender, who found that in alkaline hydrolysis of methyl, ethyl, and isopropyl benzoates, the esters had lost 0. A similar experiment carried out for acid-Catalyzed hydrolysis of ethyl benzoate showed that here too the ester lost However, alkaline hydrolysis of substimted benzyl benzoates showed no loss. This result does not necessarily mean that no tetrahedral intermediate is involved in this case. If 74 and 76 do not revert to ester, but go entirely to acid, no loss will be found even with a tetrahedral intermediate. In the case of benzyl benzoates this may very well be happening, because formation of the acid relieves steric strain. Another possibility is that 74 loses OR before it can become protonated to 75. Even the experiments that do show loss do not prove the existence of the tetrahedral intermediate, since it is possible that is lost by some independent process not leading to ester hydrolysis. To deal with this possibility. Bender and Heck measured the rate of loss in the hydrolysis of ethyl trifluorothioloacetate- 0 ... 

Sharmila M, Ramanand K, Sethunanthan N. 1981. Hydrolysis of methyl parathion in a flooded soil. 

Wolfrom, Sowden, and Lassettre measured the rate of hydrolysis of methylated cellulose in fuming hydrochloric acid at 0°C by continuous mere apt alation of the aldose group formed for each bond ruptured. 

For the delicate transesterification of a p-Lactam intermediate (for carbacephalosphorin skeleton), where originally hydrolysis of methyl ester was done homogeneously and then formation of the benzyl (or substituted benzyl) ester was done separately, Doecke et al. (1991) have devised a mild and efficient methodology using PTC. A dual use of a PT catalyst, Bu4NBr, in one pot was made in a CH2CI2 - H2O system. In the first step 5N NaOH was used, then the pH was adjusted to 7.2 to 7.8 and subsequently benzyl (or substituted benzyl) bromide was added. 

P.M. Jeffers and N.L. Wolfe, Hydrolysis of methyl bromide, ethyl bromide, chloropicrin, 1,4-dichloro-2-butene, and other halogenated hydrocarbons, in Fumigants Environmental Fate, Exposure, and Analysis, ed. J.N. Seiber, J.A. Knuteson, J.E. Woodrow, N.L. Wolfe, M.V. Yates, and S.R. Yates, ACS Symposium Series No. 652, American Chemical Society, Washington, DC, pp. 32-41 (1997). 

Attempts to hydrolyze S-b-MM under either acidic or basic conditions were unsuccessful. Reaction of S-b-MM with TsOH under the same conditions described by Brown and White (6) resulted in no reaction as evidenced by comparison of the 1H NMR and IR spectra of the product with that of the starting material. At the molecular weights and MM contents that we were working with, the S-b-MM was insoluble in the reaction medium, which may explain its lack of reactivity. Although the hydrolysis of methyl methacrylate under basic conditions is known to be quite sluggish, we nevertheless subjected S-b-MM to two days of reflux in aqueous THF in the presence of excess KOH. As expected, the product was spectroscopically identical to the starting copolymer. 

Hydrolysis of methyl sulfate Rate of hydrolysis increased... 

D-Glucose residue 1 would therefore appear as 2,3,4,6-tetramethyl-D-glucose on hydrolysis of methylated dextran D-glucose 2 as 2,3-dimethyl-D-glucose and the other three D-glucose residues as 2,3,4-tri-... 

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