Methyl trifluoroacetate, hydrolysis

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). ...

Kutsuna, S., Chen, L., Ohno, K., Tokuhashi, K., and Sekiya, A. Henry s law constants and hydrolysis rate constants of 2,2,2-trifluoroethyl acetate and methyl trifluoroacetate, Atmos. Environ., 38(5) 725-732, 2004. 

Fig. 12. First-order rate coefficients for the hydrolysis of weakly basic esters, as a function of acid concentration. Data for phenyl and methyl trifluoroacetates in HCIO, in 70% dioxan-water at 0°C (from refs. 89 and 90). and for o-nitrophenyl hydrogen oxalate in aqueous HCI at 25.5°C (from ref. 171 corrected for the reaction of the anion using pA", = 0.35).

The rate constant for the hydrolysis of t-butyl chloride at 298 K decreases as x2 increases in DMSO + water mixtures (Heinonen and Tommila, 1965). A clear-cut contrast between TA and TNAN mixtures is shown by the volumes of activation and related parameters for the solvolysis of benzyl chloride in acetone + water (TA) and DMSO + water mixtures (Fig. 57). Thus, in the latter system, the curves show no marked extrema but there is a shallow minimum in AV near x2 = 0 4. Extrema in Sm AH and T. 5m AS for the hydrolysis of benzyl chloride are also smoothed out when the co-solvent is changed from acetone to DMSO (Tommila, 1966). A similar trend is observed in the kinetic parameters for the hydrolysis of chloromethyl and methyl trifluoroacetates (Cleve, 1972a). For example, in the case of the chloro derivative, 6mACp decreases gradually over the range 0 < x2 < 0-2 for DMSO + water mixtures, whereas a minimum is observed in this range for acetone + water mixtures. 

The hydrolysis of methyl trifluoroacetate has two slow steps. increases the rate of the first slow step by providing metal-bound hydroxide ion, a better nucleophile than water. Zn " " increases the rate of the second slow step by decreasing the basicity of the group that is eliminated from the tetrahedral intermediate. 

Mechanism of Chlorination of ajS-Unsaturated Ketones in Methanol and in Trifluoroacetic Acid . Reactivity of Ethylenic Compounds. Bromination. XXXIII. Modification of Reaction Scheme in Trifluoroacetic Acid Solution [rate-determining step in CFj-COsH for bromination of RCHt CHtCHj is the disappearance (mechanism Ad%C, d) of a tight ion pair]. Solvent and Temperature Effects in the Neutral Hydrolysis of Methyl Trifluoroacetate and Chloromethyl Dichloroacetate in Dimethyl Sulphoxide-Water Mixtures . Electron Impact Studies. LiKXXVlII. Formation of an Adduct between the Trifluoroacetate Ion and Perfluoroacetic Anhydride by Ion Cyclotron Resonance . ... 

Upon carefully controlled hydrolysis with hydrochloric acid at room temperature, the corresponding serine methyl esters 4 are obtained in reasonable yields. Higher yields of 4 arc obtained by hydrolyzing with dilute trifluoroacetic acid5. In some cases, the diastereomeric ratio of 4 does not exactly correspond to the d.r. of the adduct 3, which is attributed to different kinetics in the hydrolysis of the diastereomers 4. Subsequent treatment of the methyl ester with excess 5 N hydrochloric acid and methyloxirane as an acid scavenger results in the free amino acid 54,7. 

Miki and Hachiken reported a total synthesis of murrayaquinone A (107) using 4-benzyl-l-ferf-butyldimethylsiloxy-4fT-furo[3,4-f>]indole (854) as an indolo-2,3-quinodimethane equivalent for the Diels-Alder reaction with methyl acrylate (624). 4-Benzyl-3,4-dihydro-lfT-furo[3,4-f>]indol-l-one (853), the precursor for the 4H-furo[3,4-f>]indole (854), was prepared in five steps and 30% overall yield starting from dimethyl indole-2,3-dicarboxylate (851). Alkaline hydrolysis of 851 followed by N-benzylation of the dicarboxylic acid with benzyl bromide and sodium hydride in DMF, and treatment of the corresponding l-benzylindole-2,3-dicarboxylic acid with trifluoroacetic anhydride (TFAA) gave the anhydride 852. Reduction of 852 with sodium borohydride, followed by lactonization of the intermediate 2-hydroxy-methylindole-3-carboxylic acid with l-methyl-2-chloropyridinium iodide, led to the lactone 853. The lactone 853 was transformed to 4-benzyl-l-ferf-butyldimethylsiloxy-4H-furo[3,4- 7]indole 854 by a base-induced silylation. Without isolation, the... 

For the three reactions represented in Fig. 12 the maximum rate of hydrolysis in acid represents only a mpdest acceleration, compared with the rate in initially neutral solution. Bunton and Hadwick89,90 explained the maximum for methyl and phenyl trifluoroacetate in terms of negative salt effects on both acid-catalyzed and neutral reactions. Consistent with this interpretation, it was demonstrated directly that the rate of neutral hydrolysis is decreased by added salts. The effect of added salt should be to decrease the activity of water, and perhaps also to salt in the ester. 

Hydrolysis of a methyl ether.1 Treatment of either 1 or 2 with BF3 etherate yields exclusively 3 (aklavinone). One explanation for the result is formation of a cyclic borate ester intermediate involving the C7- and C9-hydroxyl groups. Under similar conditions, trifluoroacetic acid converts either 1 or 2 into an 8 1 mixture of 3 and 7-epi-3. BF3 etherate was also used to convert the C,0-epimer of 2 into 3. 

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