Ethyl acetate alkaline hydrolysis

Under conditions of extreme acidity or alkalinity, acryhc ester polymers can be made to hydroly2e to poly(acryhc acid) or an acid salt and the corresponding alcohol. However, acryhc polymers and copolymers have a greater resistance to both acidic and alkaline hydrolysis than competitive poly(vinyl acetate) and vinyl acetate copolymers. Even poly(methyl acrylate), the most readily hydroly2ed polymer of the series, is more resistant to alkah than poly(vinyl acetate) (57). Butyl acrylate copolymers are more hydrolytically stable than ethyl acrylate copolymers (58). 

Hydrolysis of vinyl acetate is catalyzed by acidic and basic catalysts to form acetic acid and vinyl alcohol which rapidly tautomerizes to acetaldehyde. This rate of hydrolysis of vinyl acetate is 1000 times that of its saturated analogue, ethyl acetate, ia alkaline media (15). The rate of hydrolysis is minimal at pH 4.44 (16). Other chemical reactions which vinyl acetate may undergo are addition across the double bond, transesterification to other vinyl esters, and oxidation (15—21). 

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),... 

This procedure was compared with sequential extractive techniques employing alkaline hydrolysis of dried plant tissue followed by extraction of the acidified mixture with ethyl acetate. Fractions were individually evaluated for phytotoxic properties. Selected fractions from those showing a positive response were analyzed by gas-liquid chromatography. Structural identification and characterization of the individual components in these selected fractions were accomplished by gas chromatography-mass spectrometry. 

Glutarimides may be regarded as oxidized piperidines, and many drugs containing this moiety are sedatives and anticonvulsants. A spiro derivative, alonimid (105) is such a sedative-hypnotic agent. It can be prepared by K t-butoxide catalyzed biscyano-ethylation of phenylacetonitrile, leading to 101. Alkaline hydrolysis produces tricarboxylic acid 102 which is smoothly Converted to the glutaric acid anhydride (103) with acetic anhydride. Friedel-Crafts... 

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

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

Fig. 21. Logarithmic plot of the second-order rate coefficients k2) for catalysis by imidazole of the hydrolysis of various esters, against the rate coefficients for alkaline hydrolysis. The most reactive compound is acetic anhydride the other open circles represent results for acetate esters of phenols, except for the two least reactive compounds, trifluorethyl acetate, and the acetate of acetone-oxime. The closed triangles represent data for ethyl esters with activated acyl groups, with the exception of the least reactive compound, which is ethyl acetate.

In a situation where severe steric hindrance (e.g., 16,16-dimethyl-20-keto-pregnanes) prevents enol acetate formation, an alternate scheme has been devised. Condensation of ethyl oxalate at C-21 produces, after hydrolysis, the 21-glyoxylic acid this on treatment with acetic anhydride and a strong acid catalyst such as perchloric acid gives both A17(20)-enol lactone acetates. Epoxidation with peracid, and mild alkaline hydrolysis proceeds to give the 17a-hydroxy-20-ketone in a high overall yield.257... 

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... 

A quantitative assessment of the effects of head group bulk on, S k2 and E2 reactions in cationic micelles has been made.148 The kinetics of the acid-catalysed hydrolysis of methyl acetate in the presence of cationic, anionic, and non-ionic surfactants has been reported on.149 The alkaline hydrolysis of -butyl acetate with cetyltrimethylammonium bromide has also been investigated.150 The alkaline hydrolysis of aromatic and aliphatic ethyl esters in anionic and non-ionic surfactants has been studied.151 Specific salting-in effects that lead to striking substrate selectivity were observed for the hydrolysis of /j-nitrophenyl alkanoates (185 n = 2-16) catalysed by the 4-(dialkylamino)pyridine-fimctionalized polymer (186) in aqueous Tris buffer solution at pH 8 and 30 °C. The formation of a reactive catalyst-substrate complex, (185)-(186), seems to be promoted by the presence of tris(hydroxymethyl)methylammonium ion.152... 

Figure 6. Variations of E and log A with solvent composition for the alkaline hydrolysis of ethyl acetate in DMSO-water mixtures (Tommila and Murto, 1963).

The activation parameters for more complex reactions show similar patterns to that outlined above. For example, in the alkaline hydrolysis of ethyl acetate in aqueous mixtures (Tommila et al.t 1952), the second-order rate constant decreases with increasing mole fraction of ethyl alcohol, while AG increases, and AH falls to a minimum near x2 = 0-1 (Fig. 52), 5m AS having a minimum in the same region. A similar trend is observed in aqueous acetone and in... 

Figure 52. Dependence of enthalpy of activation for the alkaline hydrolysis of ethyl acetate on alcohol mole fraction in ethyl alcohol + water mixtures (Tommila et al., 1952)..

The endothermic maxima observed for apolar solutes and salts in water-rich mixtures must also contribute towards the minima in AH for alkaline ester hydrolysis in these mixtures. As before, the tendency for the rate constant to decrease is determined by the behaviour of 5m AS. Plots of AH against AS are complicated but in mixtures for which x2 < xf the data points generally fall on a straight line. Of course, there are new problems in this class of reactions. For example, the possibility arises that the rate constant is a function of quantities describing the equilibrium between, say, RO- and OH". However, the patterns which emerge indicate that this may not usually be an important consideration in water-rich mixtures. One exception may be the alkaline hydrolysis of ethyl acetate and methyl acetate (Tommila and Maltamo, 1955) in methyl alcohol + water mixtures for which AH increases gradually as x2 increases. 

Interest in the kinetics of alkaline hydrolysis of esters in DMSO + water mixtures was stimulated by the observation that the rate constant often increased gradually as x2 increased. This is observed, for example, in the alkaline hydrolysis of ethyl acetate. For higher esters, e.g. ethyl p-nitrobenzoate, the rate constant drops slightly at low x2 but then rises again until k/k x2 = 0) > 1 (Tommila, 1964). The rate of alkaline hydrolysis of esters of benzoic acid is accelerated when DMSO is added (Tommila and Palenius, 1963), as also is the rate of alkaline hydrolysis of 2,4-dinitrofluorobenzene. In the latter case the effect is less dramatic because the rate constant for spontaneous hydrolysis also increases (Murto and Hiiro, 1964). The rate constants also increase when DMSO is added to aqueous solution for reactions between hydroxide ions and benzyl chloride (Tommila... 

A careful analysis has been reported of the alkaline hydrolysis of ethyl acetate in these mixtures (Fuchs et al., 1974). The thermodynamic transfer quantities for ethyl acetate on going from water to DMSO + water mixtures together with 8mH° (OH-) show that the increase in rate constant over the range 0 < x2 < 0-3 is due to the change in AS which offsets an increase in AH. Transfer of ethyl acetate and hydroxide ions from water to the aqueous mixtures is generally endothermic but Sm AH is not negative when x2 >0 15 because 5mH is more positive than for 8mH (ester) + 8mtf ( OH-). 

---