Hydrolysis of ethyl acetate

H3PMO]204o, H4SiW,204o, and H3PW6M06O40 cannot effectively be occluded in a silica matrix because these acids are leached from the silica network in the course of the occlusion process. Titania and zirconia were both unsuitable as matrices for occlusion of HPA. 

---

Hydrolysis of Ethyl Acetate (Semi-Micro Scale)... 

In one of the earliest kinetic studies of an organic reaction earned out m the nine teenth century the rate of hydrolysis of ethyl acetate m aqueous sodium hydroxide was found to be first order m ester and first order m base... 

The hydrolysis of ethyl acetate, prepared by the reaction of ethylene with acetic acid under pressure (154), and the hydrolysis of the ethyl ester of chlorosulfonic acid (155) have been considered and found to be of Httie industrial importance. 

It is otherwise for complex reactions, for which the rate equation may or may not be simply related to the overall stoichiometric reaction. For example, the rate equation for the alkaline hydrolysis of ethyl acetate, which is a complex reaction (see Section 1.2),... 

The rate constant for the acid-catalyzed hydrolysis of ethyl acetate is... 

The rate of hydrolysis in the presence of resins increases with the number of catalytically active ions. In some reactions, the reaction rate is a linear function of the quantity of catalyst added [26,34]. Figure 1 shows the effect of varying catalyst concentration on the rate of hydrolysis of ethyl acetate. Higher values of q are shown with the larger amount of catalyst. 

Table 3 Effect of Varying Catalyst Concentration on the Hydrolysis of Ethyl Acetate (0.2 M) at 45°C...

J mol ). This is additional evidence in favor of rate limitation by inner diffusion. However, the same reaction in the presence of Dowex-50, which has a more open three-dimensional network, gave an activation energy of 44800 J mol , and closely similar values were obtained for the hydrolysis of ethyl acetate [29] and dimethyl seb-acate [30]. The activation energy for the hydrolysis of ethyl acetate on a macroreticular sulphonated cationic exchanger [93] is 3566 J mol . For the hydrolysis of ethyl formate in a binary system, the isocomposition activation energy (Ec) [28,92] tends to decrease as the solvent content increases, while for solutions of the same dielectric constant, the iso-dielectric activation energy (Ed) increases as the dielectric constant of the solvent increases (Table 6). 

Consider the following mechanism for rhe hydrolysis of ethyl acetate. Write a complete balanced equation for the overall reaction, list any intermediates, and identify the catalyst in this reaction. 

Example. A solution of ethyl acetate in pH 9.5 buffer (25°C) was assayed in triplicate several times over a 20-hour period. The data obtained are presented in Table 2. The results were plotted on semilogarthmic graph paper as shown in Fig. 3. Calculate the psuedo-first-order rate constant for the hydrolysis of ethyl acetate at pH 9.5 (25°Q. 

Fig. 3 Semilogarithmic plot of concentration versus time for the hydrolysis of ethyl acetate. (Data shown in Table 2. One standard deviation is indicated by error bars.)...

Change of electrical conductance in a reacting system involving ionic species (e.g., the hydrolysis of ethyl acetate) the reaction is carried out in a conductivity cell in an electrical circuit for measuring resistance. 

Data of the hydrolysis of ethyl acetate in the presence of a constant amount of HC1 have been obtained by Knoblauch (Z physik Chem 22 268, 1897). 

The hydrolysis of ethyl acetate (B) with an alkaline hydroxide (A] non-aqueous solutions is believed to have the third order rate equation... 

Fig. 6 Hydrolysis of ethyl acetate over Zr[(03P0H) (03PCi2H25)7.j2 as a function of x.

This agrees with A. E. Leighton s statement that when sodium carbonate is present in water used in steam boilers, the boiled water contains sodium hydroxide. J. Shields and K. Kolichen have measured the degree of hydrolysis of aq. soln. of sodium carbonate the former from measurements on the rate of hydrolysis of ethyl acetate, the latter from the decomposition of diacetone-alcohol, CH3.CO.CH2.C(CH3)2OH 2CH3.CO.CH3. The percentage hydrolysis of soln. of sodium carbonate of different cone, by the two methods are of the same order of magnitude ... 

Activation parameters that have been measured for Aal1 reactions are generally consistent with a unimolecular rate-determining step. The volume of activation for the hydrolysis of f-butyl acetate in 0.01 M HCI at 60°C is zero, within experimental error70. No significant change in rate is observed from atmospheric pressure up to 2 kbar, although this increase in pressure almost doubles the rate of hydrolysis of ethyl acetate in 0.1 M HCI at 35°C. 

The effects of added salts are shown in Fig. 8. Sodium chloride has a small positive effect on the hydrolysis rate, and sodium chloride and sodium perchlorate have a similar, rather larger, effect on the rate of lactone formation. This is the expected result, for many salts increase the protonating power of the medium as measured by Hammett s acidity function116, and thus assist acid-catalyzed reactions. Sodium perchlorate, unusually, has a small negative effect on the hydrolysis rate. Qualitatively similar results have been found by Bunton et al,56, who studied the effects of added salts on the acid-catalyzed hydrolysis of ethyl acetate. Added lithium and sodium chloride assist the Aac2 hydrolysis of ethyl acetate, but the perchlorates have essentially no effect. In each case the effect is a little more positive than for y-butyrolactone hydrolysis, and, in particular, chloride anions appear to assist Aac2 hydrolysis more effectively than do the perchlorates. 

Lane38 measured the rate of hydrolysis of ethyl acetate at 25°C in 11 -79% sulphuric acid by both spectrophotometric and dilatometric techniques. He also measured spectrophotometrically the concentration of the conjugate acid of the ester in solution by measuring the absorptivity at 190 nm, and extrapolating to zero time, and by the change in the chemical shift of the acetyl protons. He found a linear relation between the ionization ratio and Hammett s acidity function... 

The acid-catalyzed hydrolysis of orthoesters is very much faster than that of esters. The second-order rate coefficient for the hydrolysis of ethyl acetate is of the order of 10"4 1-mole-1-sec1 at 25°C, whereas that for the hydrolysis of ethyl orthoacetate103 is of the order of 104 l-mole-1-sec 1, and that for the breakdown of a monoalkyl orthoester must be faster still. If the breakdown of the tetrahedral intermediate is partially rate-determining in acid-catalyzed ester hydrolysis, therefore, its concentration must be very small that is, the equilibrium for its formation must be highly unfavourable. This... 

This sensitivity to substitution of neutral hydrolysis means that the pH-independent reaction gradually becomes more important than the hydroxide reaction at the high pH end of the region, and becomes much more rapidly more important than acid-catalyzed hydrolysis at low pH. Thus from Fig. 13, the acid-catalyzed reaction can be seen to be significant for the hydrolysis of ethyl acetate between pH 4 and 5, and for phenyl acetate about pH 2 but for 2,4-dinitrophenyl acetate the acid-catalyzed reaction is not detectable at pH 1, and is presumably important only in relatively strong acid. It seems certain that this fast neutral hydrolysis is at any rate a partial explanation for the low efficiency of acid catalysis in the hydrolysis of very weakly basic esters, such as the trifluoroacetates and oxalates, in moderately concentrated acid (see p. 145). 

Fig. 15. Effects of added solvents on the rate coefficients for alkaline hydrolysis of ethyl acetate...

Oxyanions of sufficient basicity will catalyze the hydrolysis of all but the least reactive esters but since the latter include the esters of the common aliphatic alcohols, early attempts to detect the reaction were negative or inconclusive. Dawson and Lowson274, claimed to have detected catalysis by acetate ion of the hydrolysis of ethyl acetate as early as 1927, but the extent of catalysis observed was too small to rule out the possibility that salt or solvent effects were, in fact, responsible. 

The transition from nucleophilic to general base catalysis of ester hydrolysis has been demonstrated by Kirsch and Jencks300 for attack by imidazole on a series of acetate esters. Their data are given in Table 41, and include a figure for the catalysis by imidazole of the hydrolysis of ethyl acetate. This must... 

Cs2.5 in water is hardly separable by filtration because of its very fine particle size. Cs2.5/Si02 prepared by the hydrolysis of ethyl orthosilicate in the presence of colloidal Cs2.5 is efficient for the hydrolysis of ethyl acetate, although it is less active than Amberlyst 15 (200). 

A characteristic reaction of ethyl acetate is hydrolysis, the reverse of the reaction in Problem 13.52. Write the equilibrium equation for hydrolysis of ethyl acetate, and use the data in Problem 13.52 to calculate Kc for the hydrolysis reaction. 

The 3-4 Cals, here represent the heat of admixture of a mol of ammonia with water, and this is much greater than the heat of admixture of ammonia with other liquids which do not react chemically with the ammonia. There is also a possibility that ammonia hydrates. NH3.nH20, are formed, vide infra and a possibility that the ammonium hydroxide is ionized NH OH NH +OH. In agreement with the assumption that ammonium hydroxide is formed which acts as a weak base, the liquid tastes alkaline it reddens turmeric colours the juice of violets green and colours litmus, etc., the same as do soln. of the alkali hydroxides. These changes of colour disappear on exposure to air owing to the volatilization of the ammonia— the volatile alkali of the early chemists. The feeble character of ammonium hydroxide as a base is evidenced by its heat of neutralization with acids which is about 1-5 Cals, less than is the case with potassium or sodium hydroxides like other weak bases, the soln. cannot be satisfactorily titrated with phenolphthalein S. Arrhenius found that its effect on the hydrolysis of ethyl acetate is about 40 times leBS than that of sodium hydroxide and the electrical conductivity of aq. soln. of... 

---