Prediction of ortho substituent effect in alkaline hydrolysis of phenyl esters of substituted benzoic acids in aqueous acetonitrile

The second-order rate constants k for the alkaline hydrolysis of phenyl esters of meta-, para- and ortho-substituted benzoic acids, X-C₆H₄CO₂C₆H₅, in aqueous 50.9% acetonitrile have been measured spectrophotometrically at 25°C. The log k values for meta and para derivatives correlated well with the Hammett σ_m,p substituent constants. The log k values for ortho-substituted phenyl benzoates showed good correlations with the Charton equation, containing the inductive, σ_I, resonance, σ^○ _R, and steric, E _s ^B, and Charton υ substituent constants. For ortho derivatives the predicted (log k _X)_calc values were calculated with equation (log k _ortho)_calc = (log k ^H _AN)_exp + 0.059 + 2.19σ_I + 0.304σ^○ _R + 2.79E _s ^B ? 0.0164ΔEσ_I — 0.0854ΔEσ^○ _R, where DE is the solvent electrophilicity, ΔE = E _AN — E _H20 = ?5.84 for aqueous 50.9% acetonitrile. The predicted (log k _X)_calc values for phenyl ortho-, meta- and para-substituted benzoates in aqueous 50.9% acetonitrile at 25°C precisely coincided with the experimental log k values determined in the present work. The substituent effects from the benzoyl moiety and aryl moiety were compared by correlating the log k values for the alkaline hydrolysis of phenyl esters of substituted benzoic acids, X-C₆H₄CO₂C₆H₅, in various media with the corresponding log k values for substituted phenyl benzoates, C₆H₅CO₂C₆H₄-X.     

Changing mechanisms in the beta-cyclodextrin-mediated hydrolysis of phenyl esters of perfluoroalkanoic acids

The rate of hydrolysis of esters CF(3)(CF(2))(n)COOPh (1 (n = 1), 2 (n = 2), and 3 (n = 6)) was measured at pH 6.00 and at pH higher than 9.00 in the presence of beta-cyclodextrin (beta-CD). For compounds 1 and 2 the reaction rate decreases as the beta-CD concentration increases, and they show saturation effects at all pH. It is suggested that the substrate forms an inclusion complex with cyclodextrin. Analysis of the rate data allows calculation of the association equilibrium constant, K(CD), the rate constant for the reaction of the included compound, k(c), and K(TS) which is the hypothetical association equilibrium constant for the transition state of the cyclodextrin-mediated reaction. The dependence of log K(CD) and log K(TS) with the number of atoms in the chain is different. We suggest that the reactions of 1 and 2 take place with the perfluorinated alkyl chain included in the cavity, whereas the transition state for the reaction of phenyl trifluoroacetate involves a complex with the aryl ring inside the cavity. At low pH the inhibition comes from the protection of the carbonyl group toward nucleophilic attack by water. In basic pH the reaction of HO(-) as an external nucleophile is also inhibited. The cyclodextrin-mediated reaction involves the ionized OH group at the rim of the cyclodextrin cavity with poor efficiency due to an unfavorable orientation of the substrate in the complex. On the other hand, the reaction of compound 3 is strongly accelerated by cyclodextrin because the association of the substrate with cyclodextrin competes with the monomer-aggregate equilibrium and at high enough cyclodextrin concentration the main species present in solution is the complex between 3 and cyclodextrin.     

Kinetics of alkaline hydrolysis of esters of phosphorus acids in micellar and hexagonal phases in the cetyldimethylethylammonium bromide—NaOH—water system

The influence of micellar (Mi) and hexagonal (E) mesophases of the cetyldimethylethylammonium bromide—NaOH—water system (I) on the rates on alkaline hydrolysis ofO-p-nitrophenyl-O,O-diethyl phosphate (2),O-p-nitrophenyl-O-ethylethyl phosphonate (3), andO,O-di(p-nitrophenyl)methyl phosphonate (4) was studied by UV spectrophotometry. The binding constants of the substrates, critical micelle concentrations, and rate constants of reactions in the micellar phase were determined. In micellar solutions of systemI, a tenfold increase in the rates of alkaline hydrolysis of2–4 was observed. An increase in the degree of medium ordering during the formation of the E-phase results in a twofold acceleration of alkaline hydrolysis of2 and3 and in the inhibition of this process in the case of4. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1499–1504, August, 1998.     

Thioethynyl esters of phosphorus acids

The results of searching for the methods of synthesis of substituted thioethynyl monothio- and dithiophosphates, which are of interest as physiologically active compounds, are summarized. The preparative method for the synthesis of thioesters of O,O-dialkylmonothiophosphoric acids of a specific type was developed: the reaction of substituted ethynyl bromides with potassium salts of the corresponding monothiophosphoric acids in the presence of an equimolar amount of CuCl. These reactions occur through the stage of formation of Cu^I salts of the corresponding monothiophosphoric acids and are accompanied by redox processes leading to the formation of free radicals. The modified method for the synthesis of substituted thioethynyl monothio- and dithiophosphates is the reaction of Cu^I salts of these acids with the corresponding ethynyl bromides.     

Reactivity of triesters of phosphoric acid in alkaline hydrolysis

Conclusions A difference in the alkaline hydrolysis rates of the triesters of phosphoric acid is determined by the sum of the induction effects of the alcohol radicals; the effect of the cleaved and remaining groups is equivalent.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2595–2596.     

Selenium-containing esters of pentavalent phosphorus acids

New carboranyl selenophosphates and selenophosphonates have been prepared. A series of S--carboranylselenoethyl esters of pentavalent phosphorus acids has been prepared. These compounds hold interest as potentially physiologically active compounds.Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 7, pp. 1653–1655, July, 1990.     

o-Carboranyl-containing esters of pentavalent phosphorus acids

Conclusions Some new carboranyl esters of pentavalent phosphorus acids were synthesized from the appropriate propargyl esters and decaborane.See [1] for preliminary communication.Translated from Izvestiya Akademii NaukSSSR, Seriya Khimicheskaya, No. 11, pp. 2640–2644, November, 1983.     

Catalysis of the hydrolysis of esters of phosphorus acids byn-decylammonium chloride /n-decylamine mixed micelles

The effect ofn-decylammonium chloride/n-decylamine mixed micelles on the rate of hydrolysis of aryl esters of acids of four-coordinate phosphorus was studied spectrophotometrically. The shape of the concentration curves is characteristic of the micellar catalysis reactions. The binding constants of the substrate, critical micelle concentrations, and the rate constants in the micellar phase were determined. A specific effect of the structure of substrates on these parameters was shown.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 2003–2006, August, 1996.     

Kinetics of the alkaline hydrolysis of 3-sulfolanol phenyl ethers

A scheme for the elimination of aryloxy groups via an ElcB mechanism is proposed on the basis of data on the kinetics of the alkaline hydrolysis of 3-sulfolanol phenyl ethers in H₂O and D₂O.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1200–1203, September, 1974.     

Catalytic activity of aminomethylated calix[4]resorsinolarene aggregates in hydrolysis of esters of phosphorus acids

The reaction kinetics of aminomethylated calix[4]resorcinolarenes (AMC) withp-nitrophenyl esters of phosphorus acids (EPA) in a water—DMF solution (30 vol.% DMF) was studied by spectrophotometry and³¹P NMR spectroscopy in the presence and absence of the nonionic surfactant Triton X-100. The AMC form aggregates of micellar and nonmicellar types and are the catalysts for EPA hydrolysis. The catalytic activity of the aggregates depends on their structure, pH of the medium, and the nature of the solvent. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1361–1365, August, 2000.     

Hydrotrope-induced autocatalysis in the biphasic alkaline hydrolysis of aromatic esters

The alkaline hydrolysis of aromatic esters exhibits autocatalytic kinetics when performed under two-phase conditions without any mixing solvent. The molecular structures of such aromatic esters determine whether the autocatalysis occurs or not. It has been established that enhancing the solubility of the hydrophobic ester in water by the hydrotropic salts yielded by the hydrolysis itself accelerates the apparent reaction rate. By kinetically independent measurements, the solubilization process of the ester was verified to be the rate-determining step. It has been observed that the solubilization process can be influenced by factors such as the initial addition of hydrotropic salt, the volumetric ratio of the oil/aqueous phase, and the concentration of alkali.     

A simple method for the alkaline hydrolysis of esters

A very mild and rapid procedure for the efficient alkaline hydrolysis of esters in non-aqueous conditions has been developed, by the use of dichloromethane/methanol (9:1) as solvent. This method conveniently provides both carboxylic acids and alcohols from the corresponding esters and sodium hydroxide in a few minutes at room temperature. A plausible reaction mechanism is proposed.     

Reactivity of supramolecular systems based on calix[4]resorcinarene derivatives and surfactants in hydrolysis of phosphorus acid esters

The formation of mixed micelles of amphiphilic calix[4]resorcinarenes with aminomethyl (AMC, PAMC), tris(hydroxymethyl)amide (THAC) fragments and the cationic surfactant cetyl trimethylammonium bromide (CTAB) in water and aqueous DMF solutions (10-50% DMF) leads to the decrease of the critical micelle concentration of the systems and the increase of the size of the mixed micelles in comparison with CTAB micelles. The catalytic activity of the mixed systems in the hydrolysis of phosphorus acid esters is higher than those of CTAB micelle and AMC, PAMC or THAC aggregates.     

Estimation of the catalytic activity of onium chlorides and bromides in the alkaline hydrolysis of amino acids esters

Relations were investigated between the structure of a series of onium salts, rates of alkaline hydrolysis catalyzed by the salts of 4-nitrophenyl N-benzyloxycarbonylglycinate in a two-phase liquid-liquid system, and the value of the standard exchange enthalpy of anions in ion pairs with the catalyst cation calculated by the semiempiric PM3 method. The catalytic activity of ammonium, phosphonium, pyridinium, imidazolium, and benzimidazolium salts in a wide range of cation structures varies in parallel with the enthalpy of formation of the active form of the catalyst by the exchange of the anion with a hydroxide ion.