Arrhenius parameters for the alkaline hydrolysis of esters in aqueous solution. Part III. Methyl betaine methyl ester

The second-order rate constants k2 for alkaline hydrolysis of phenyl esters of meta-, para- and ortho-substituted benzoic acids, X-C6H4CO2C6H5 (X = H, 3-Cl, 3-NO2, 3-CH3, 4-NO2, 4-Cl, 4-F, 4-CH3, 4-OCH3, 4-NH2, 2-NO2, 2-CN, 2-F, 2-Cl, 2-Br, 2-I, 2-CH3, 2-OCH3, 2-CF3, 2-NH2), and of substituted phenyl esters of benzoic acid, C6H5CO2C6H4-X (X = 2-I, 2-CF3, 2-C(CH3)3, 4-Cl, 4-CH3, 4-OCH3, 4-NH2), have been measured spectrophotometrically in water at 25 °C. The substituent effect in alkaline hydrolysis of phenyl esters of para-substituted benzoic acids, similar to that for ethyl esters of para-substituted benzoic acids, was found to be precisely described by the Hammett relationship (ρ = 1.7 in water). The log k value for alkaline hydrolysis of phenyl and ethyl esters of meta-, para- and ortho-substituted benzoic acids, X-C6H4CO2R, was nicely correlated with log km,p,ortho = log ko + (ρ)m,pσ + (ρI)orthoσI + (ρ°R)orthoσ°R + δorthoEsB where σ, σI, σ°R are the Hammett polar, Taft inductive and Taft resonance (σ°R = σ° - σI) substituent constants, respectively. EsB is the steric scale for ortho substituents calculated on the basis of the log k values for the acid hydrolysis of ortho- substituted phenyl benzoates in water owing to the ortho substituent in the phenyl of phenyl benzoates. In water, the main factors responsible for changes in the ortho substituent effect in alkaline hydrolysis of phenyl and ethyl esters of ortho-substituted benzoic acids, X-C6H4CO2R, were found to be the inductive and steric factors while the role of the resonance term was negligible ((ρ°R)ortho ca. 0.3). In alkaline hydrolysis of substituted benzoates in neat water, the ortho inductive effect appeared to be 1.5 times and steric influence 2.7 times higher than the corresponding influences from the ortho position in the phenyl of phenyl benzoates. The contributions of the steric effects in alkaline hydrolysis of esters of ortho-substituted benzoic acids was found to be approximately the same as in acid hydrolysis of esters of ortho-substituted benzoic and acid esterification of ortho-substituted benzoic acids.

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The Chemical Evolution of a Nitrogenase Model, 20 Alkyl Molybdates(VI) and the Mechanism of Hydrocarbon Production by Nitrogenase [1]

Zeitschrift für Naturforschung B ◽

10.1515/znb-1982-0320 ◽

1982 ◽

Vol 37 (3) ◽

pp. 380-385 ◽

Cited By ~ 12

Author(s):

G. N. Schrauzer ◽

Laura A. Hughes ◽

Norman Strampach

Keyword(s):

Aqueous Solution ◽

Alkaline Hydrolysis ◽

Room Temperature ◽

Bond Cleavage ◽

Model Compounds ◽

Hydrocarbon Production ◽

Acidic Solutions ◽

Reducing Conditions ◽

Hydrolysis Of ◽

Derivatives Of

Abstract Colorless alkylmolybdates(VI) of composition R-MoO3-are generated in aqueous solutions by the alkaline hydrolysis of complexes R-Mo(Bpy)(0)2Br(Bpy = 2,2′-bipyridyl, R = CH3 and higher alkyl). At room temperature in alkaline aqueous solution, the new organometallic derivatives of oxomolybdate(VI) are remarkably resistant against Mo-C bond hydrolysis. Decomposition occurs more rapidly on heating, affording unrearranged alkanes according to the eq.: R-MoO3- + OH-→RH + Mo04=. In acidic solutions, the methylmolybdate(VI) species decomposes with the formation of a mixture of methane and ethane while higher alkylmolybdates carrying hydrogen in the β-position relative to molybdenum undergo Mo-C bond heterolysis by way of β-elimina-tion: R-CH2CH2-MoO3 → Mo+4 (aq) + H+ + R-CH = CH2. The Mo-C bond of alkylmolybdates is resistant to oxidants but is very sensitive to cleavage under reducing conditions. Reductive Mo-C bond cleavage occurs particularly rapidly in the presence of thiols and reduced ferredoxin model compounds. The latter reactions simulate the terminal steps of hydrocarbon producing reactions of nitrogenase with alternate substrates such as CN-, R-CN or R-NC, confirming previous mechanistic conclusions concerning the mechanism of nitrogenase action.

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Theoretical Study on the Alkaline Hydrolysis of Methyl Thioacetate in Aqueous Solution

The Journal of Physical Chemistry A ◽

10.1021/jp204658w ◽

2011 ◽

Vol 115 (46) ◽

pp. 13523-13533 ◽

Cited By ~ 7

Author(s):

Chein-Wei Fu ◽

Thy-Hou Lin

Keyword(s):

Aqueous Solution ◽

Alkaline Hydrolysis ◽

Theoretical Study ◽

Hydrolysis Of

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The acid-catalysed hydrolysis of α-methylallyl acetate in aqueous solution

Australian Journal of Chemistry ◽

10.1071/ch9681727 ◽

1968 ◽

Vol 21 (7) ◽

pp. 1727

Author(s):

RA Fredlein ◽

I Lauder

Keyword(s):

Aqueous Solution ◽

Reaction Products ◽

Arrhenius Parameters ◽

Crotyl Alcohol ◽

Kinetics Of ◽

Hydrolysis Of ◽

Tracer Experiments

The kinetics of the acid-catalysed hydrolysis of a-methylallyl acetate in aqueous solution have been studied over the range 30-100�. Oxygen-18 tracer experiments reveal the mechanism to be solely Aac2 and the Arrhenius parameters are consistent with this conclusion. Crotyl alcohol is observed in the reaction products. The formation of rearranged alcohol is explained by allylic isomerization of the α-methylallyl alcohol produced by the hydrolysis.

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