Spontaneous hydrolysis of phenyl

Micellar Effects on the Spontaneous Hydrolysis of Phenyl Chloroformate 133... 

In contrast to reaction (5-158), addition of micelle-forming surfactants can also slow down chemical reactions. For example, the spontaneous hydrolysis of phenyl chloroformate at 25 °C according to Eq. (5-158a) is retarded by a factor of ca. 16 on addition of sodium dodecylsulfate (SDS) above the one. Below the erne, the SDS... 

Rodriguez, A., Graciani, M. del M., Munoz, M., Moya, M.L. Water-ethylene glycol alkyltrimethylammonium bromide micellar solutions as reaction media study of spontaneous hydrolysis of phenyl chloroformate. Langmuir 2003, 79(18),... 

The effects of [cationic micelles] (micelle-forming surfactants are hexade-cyltrimethylammonium bromide, CTABr, tetradecyltrimethylammonium bromide, TTABr, and dodecyltrimethylanunonium bromide, DTABr) on the rates of spontaneous hydrolysis of phenyl chloroformate in water-ethanediol (ED) solvents have been rationalized in terms of pseudophose (PP) model, i.e.. Equation 3.2 with replaced by Experimentally observed values of k M decrease... 

The rate of spontaneous hydrolysis of phenyl chloroformate decreases with increase in the concentration of micelles of various anionic, nonionic, and cationic surfactants. A comparison of the kinetic data in nonionic micellar solutions to those in anionic and zwitterionic micellar solutions makes it clear that charge effects of micelles is not the only factor responsible for the variations in the reaction rates. Depletion of water in the interfacial region and its different characteristics as compared to bulk water, the presence of high ionic concentration in the Stem layer of ionic micelles, and differences in the stabilization of the reactant state and the transition state by hydrophobic interactions with surfactant tails can also influence reactivity. 

An elegant method to suppress the undesired spontaneous hydrolysis of a 5(47/)-oxazolone in aqueous media uses a lipase-catalyzed alcoholysis reaction. Of particular importance is the synthesis of /crt-leucine, a non-proteinogenic a-amino acid that has found widespread use both as a chiral auxiliary and as a component of potentially therapeutic pseudopeptides. Racemic 4-/ert-butyl-2-phenyl-5(47/)-oxazolone 238 was submitted to Mucor miehei catalyzed alcoholysis using butanol as a nucleophile. Addition of a catalytic amount of triethylamine promoted in situ racemization. In this way, the enantiomericaUy pure butyl ester of (5)-A-benzoyl-/ert-leucine 239 was obtained in excellent yield (Scheme 7.75). 

Kinetic measurements have indicated that neighbouring acetamido-group participation occurs in the spontaneous hydrolysis and methanolysis of 2-carboxy-phenyl 2-acetamido-2-deoxy-jS-D-glucopyranoside and in the spontaneous hydrolysis of 2,4-dinitrophenyl 2-acetamido-2-deoxy-j8-D-glucopyranoside and... 

The expression of the rate constant for the hydrolysis of phenyl-substituted styrene oxides 1 to their corresponding glycols 2 is given by Eq. 11.1, where is the first-order rate constant for flie spontaneous (non-catalyzed) reaction, ka is the second-order rate constant for the hydronium ion-catalyzed reaction and is the second-order rate constant for the hydroxide-catalyzed reaction. 

Phenols with an appropriate leaving group in the benzylic position such as fluoride may form QMs by spontaneous hydrolysis, possibly catalyzed by a basic amino acid residue as shown in Scheme 10.2c. Evidence for this process was obtained with 4-(fluoromethyl)phenyl phosphate involving initial enzymatic hydrolysis of the phosphate followed by nonenzymatic formation of a QM.11 Similarly, several lines of evidence demonstrate nonenzymatic QM formation from 4-trifluoromethylphenol under physiologic conditions.12... 

Figure 2.5 Enzymatic resolution of racemic glycidyl phenyl ether (10 mM) by partially purifled enzyme in Ifis-HCl buffer (pH 7.5). Part A effect of temperature on EH activity with either ( ) Tween-80 (0.5%, w/v) or ( ) DMSO (5%, v/v) (A) represents spontaneous hydrolysis without enzyme. Part B residual EH activity after incubation at the indicated temperatures for 1 h with ( ) 5% (v/v) DMSO or ( ) 0.5% (w/v) Tween-80, or (0) without additives. Part C time-course of epoxide enantiomers (i )-GPE ( , o) and (S)-GPE ( , 0), in the presence of (o, <>) DMSO (5%, w/v) or ( , ) Tween-80 (0.5%, w/v).

Alkylation and Arylation. The 5-methylation of thioamides by diazomethane is catalysed by silica gel. 5-Phenyl derivatives of thiobenzanilides are obtained in high yield by radical arylation with nitrosoacetanilide or phenylazotriphenyl-methane. Thiols are made from alkyl (or cycloalkyl, or aralkyl) halides by their reaction with dimethylthioformamide and treatment of the imidium ester with methanol other methods of hydrolysis lead to side-reactions, giving impure products. Mono- and bi-protic thiocarboxamides condense with ethyl bromo-cyanoacetate and one equivalent of NaOEt with spontaneous separation of sulphur and the formation of ff-amino-cr-cyano-acrylates, as shown in reaction (5). The... 

Al-Lohedan, H.A., Al-Hassan, M.l. Micellar effects upon spontaneous and alkaline hydrolysis of t-hutyl phenyl carbonate. Bull. Chem. Soc. Jpn. 1990, 63( 10), 2997-3000. 

Michael additions to acceptor-substituted dienes are often followed by (spontaneous or induced) cyclizations. This was already noted by Vorlander and Groebel4 who obtained a substituted 1,3-cyclohexanedione by treatment of 6-phenyl-3,5-hexadien-2-one with diethyl malonate (equation 5). Obviously, the 1,4-addition product which is formed initially then undergoes cyclization, ester hydrolysis and decarboxylation. Similarly, reaction of methyl sorbate with methyl 4-nitrobutyrate gave the 1,6-adduct which was reductively cyclized to 6-methyl-l-azabicyclo[5.3.0]decane18 (equation 6). 

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