Hydrolysis rate laws

Hughes and Ingold observed that the hydrolysis of tert butyl bromide which occurs readily is characterized by a first order rate law... 

For example the hydrolysis of optically active 2 bromooctane in the absence of added base follows a first order rate law but the resulting 2 octanol is formed with 66% inversion of configuration... 

The acid-catalyzed hydrolysis of 2-alkoxy-2-phenyl-l,3-dioxolanes has been studied. The initial step is rate-determining under eertain eonditions and is deseribed by the rate law given below, whieh reveals general acid catalysis. 

To conclude this section, we shall consider a more complex example, the pH effects on the hydrolysis of aspirin, acetylsalicylic acid.14,16 The pH profile is given in Fig. 6-4 for the reaction and rate law... 

The pH profile for the hydrolysis of aspirin. The numbers designate four regions for the respective terms in the rate law, Eq. (6-104). 

Reaction scheme. Propose reaction steps consistent with the rate law for the hydrolysis of benzhydryl chloride relate a and /3 to the rate constants. 

Rate law and mechanism. Propose a mechanism for the hydrolysis of trimethylbenzim-idate to account for the rate law 26... 

Specific and general acid catalysis. Formulate the rate law for the acid-catalyzed hydrolysis reaction42... 

A slow, second stage leads to metallic gold. The rate law was determined, under conditions unfavourable to hydrolysis of chloraurate ion, to be... 

The rate law of the oxidation by Fe(III) is dependent on the ratio of the concentrations of the reactants. When peroxide is in excess and when the acidity is sufficient to suppress hydrolysis of Fe(IlI) the rate expression... 

Recent kinetic studies on thiophosphoric aryl ester dianilides suggest analogous decomposition. The rate law observed is in agreement with a hydrolysis scheme in which both the monoanion and the dianion decompose to metaphosphorothioimi-date and its anion, respectively, which then react fast with water133). 

Studies of the base-hydrolysis mechanism for hydrolysis of technetium complexes have further been expanded to an octahedral tris(acetylacetonato)techne-tium(III) [30], Although a large number of studies dealing with base hydrolysis of octahedral metal(III) complexes have been published [31], the mechanism of the tris(acetylacetonato)metal complex is still unclear. The second-order base hydrolysis of the cationic complex tris(acetylacetonato)silicon(IV) takes place by nucleophilic attack of hydroxide ion at carbonyl groups, followed by acetylacetone liberation, and finally silicon dioxide production [32], The kinetic runs were followed spectrophotometrically by the disappearance of the absorbance at 505 nm for Tc(acac)3. The rate law has the following equation ... 

A mechanism for a pseudo-first-order reaction involving the hydrolysis of substrate S catalyzed by acid HA that is consistent with the observed rate law rs = kohscs, is as follows ... 

Compare the properties (spectral and hydrolysis rate) of the intermediate with those of Fe(C204) generated from Fe + (excess) and CjO. Consider the role of ion pairs and triplets in understanding the rate law. 

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. 

AF values for cyanide attack at [Fe(phen)3] +, [Fe(bipy)3] + and [Fe(4,4 -Me2bipy)3] " in water suggest a similar mechanism to base hydrolysis, with solvation effects dominant in both cases. Cyanide attack at [Fe(ttpz)2] , where ttpz is the terdentate ligand 2,3,5,6-tetrakis(2-pyridyl)pyr-azine, follows a simple second-order rate law activation parameters are comparable with those for other iron(II)-diimine plus cyanide reactions. Interferences by cyanide or edta in spectro-photometric determination of iron(II) by tptz may be due to formation of stable ternary complexes such as [Fe(2,4,6-tptz)(CN)3] (2,4,6-tptz= (66)). ... 

Detailed kinetic studies revealed that glycine methyl ester and phenylalanine methyl ester in glycine buffer at pH 7.3 undergo a facile hydrolysis catalyzed by cupric ion (11). Under these conditions the reactions closely follow a first-order rate law in the substrate. Using these kinetic data it is possible to compare the rates of hydrolysis of DL-phenylalanine ethyl ester as catalyzed by hydronium, hydroxide, and cupric ion (see Table III). 

Organonickel(II) species are believed to be formed during the reaction between [Ni(TMC)] and primary alkyl halides, and subsequently undergo hydrolysis with cleavage of the Ni—C bond. Kinetic data measured in the presence of excess alkyl halide indicate a rate law -dlNi1 (TMC)+]/cft = MNi (TMCr][RX]. The rate constants increase for R and X in the order methyl < primary < secondary < allyl < benzyl halides and Cl < Br < I (133, 140). This suggests that the rate-determining step is electron transfer from the Ni(I) complex to R—X via an inner-sphere atom-transfer mechanism (143). 

Having established that 1 catalyzes the hydrolysis of orthoformates in basic solution, the reaction mechanism was probed. Mechanistic studies were performed using triethyl orthoformate (70) as the substrate at pH 11.0 and 50 °C. First-order substrate consumption was observed under stoichiometric conditions. Working under saturation conditions (pseudo-0 order in substrate), kinetic studies revealed that the reaction is also first order in [H+] and in [1]. When combined, these mechanistic studies establish that the rate law for this catalytic hydrolysis of ortho-formates by host 1 obeys the overall termolecular rate law rate = k[H+][Substrate][l], which reduces to rate = k [H ][l] at saturation. 

A further conclusion that we may draw from Table 13.5 is that the SN2 reactions of aliphatic halides with OH" should be unimportant at pH values below about 10. Since the hydrolysis of a carbon-halogen bond is commonly not catalyzed by acids, one can assume that in most cases, the hydrolysis rate of aliphatic halides will be independent of pH at typical ambient conditions. Hence, regardless of whether hydrolysis occurs by an SN1 or SN2 mechanism (or a mixture of both, see below), the reaction may be described by a first-order rate law. The first-order rate constant is then commonly denoted as N (= kmo. [HzO]) to express neutral hydrolysis. Note that if the... 

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