Kinetics of the saponification of diethyl adipate

Abstract

Much of chemical reaction engineering theory depends upon the existence of real reaction systems which possess simple order rate laws-first-order irreversible, secondorder reversible, etc. However, the experimentalist faced with the necessity of obtaining accurate kinetic data for the implementation of such theory often finds it difficult to find real systems for which such data exists. The intent of this note is to present such data for the case of a secondorder, irreversible, consecutive homogeneous reaction in the liquid phase, namely, the saponification of diethyl adipate. A vital part of such an exposition is the analysis of the accuracy of the model parameters, the possible competing reactions, the interaction with other rate processes such as heat and mass transfer, and the analytical scheme.Ingold ( 1930, 1931), Frost andSchwemer (1952), andWestheimer et al. (1942) give experimental values of the rate constants for the saponification of diethyl adipate. These authors studied many diesters at a single temperature to obtain the effects of various substituents on reaction rates and in particular the rate constants for the saponification of diethyl adipate with sodium hydroxide. The results of these investigations are shown in Table 1. adipate is present as diester.Since the caustic and adipate solutions used unavoidably are in contact with air, the question of the carbonatebicarbonate system influence arises. These react ions are Equilibrium data for the above reactions is given by Roques (1964). The effect of the presence of carbonate is treated under Error Analysis. CHEMICAL ANALYSIS OF REACTION PRODUCTSThe reaction can be quenched by allowing ieactor effluent to flow into weighed flasks containing knciwn quantities of hydrochloric acid. This effectively removes hydroxyl ion. Subsequent reweighing and a previois density determination allowed direct calculation of sample volumes. The original hydroxyl ion concentration is also easily determined by back-titration with standard sodium hydroxide. The end point was calculated to occur near pH 7.3. Following the work of Frost and Schwemer ( 1952), bromthymol blue indicator having a color change from yellow to blue between pH 6.8 and 7.5 was used.Experimental titration curves using a pH meter verified the applicability of this indicator. kl( CHz) 4 (COOCzH5) 2 + NaOH + Ingild (1930, 1931) employed benzene and pentane to extract all unreacted ester from a mixture of diethyl adipate, monoethyl adipate, and adipate ion. His work showed that benzene extracts all the diester and a small (CHz)4(C00Na) (C00C2H5) + C2H50H( 1 )The reactions are irreversible in alkaline solution due to the stabilizing effect caused by resonance of the carboxyl ion, as discussed by Geissman (1959). It is perhaps unfortunate that pure diester is rarely available. Rather, a small amount of hydrolysis can occur in the diester solution fraction of monoester from aqueous solution. The least square fit of the data of this study gives (CR)henzene phase = 0.0033 (CR)aquenus pha.e (8)After extractio...

Modification of Consecutive-Competitive Reaction Selectivity by Periodic Operation

“…Considering both the series and the parallel characteristics of consecutive-competitive reactions, it appears that temperature fluctuations in the reactor might improve selectivity provided the first reaction's activation energy exceeds that of the second reaction. This relationship has been reported to apply for the saponification of diethyl adipate, which is a two-step consecutive-competitive reaction (A = diethyl adipate, B = sodium hydroxide, P7 = sodium monoethyl adipate, P2 = sodium adipate) with report rated constants (Newberger and Kadlec, 1973) given by In order to estimate approximately the potential improvements that might be achieved by temperature cycling for this reaction, it is useful to compare the maximum yield for steady-state operation with the maximum yield which is obtained when the reactor is operated cyclically but with the same average temperature. In this introductory discussion for this example, it will be assumed that the reactor temperature can be adjusted at will instantaneously.…”

Effect of Temperature and Alkali Solution to Activate Diethyl Carbonate for Improving Rheological Properties of Modified Hydroxyethyl Methyl Cellulose

“…Further saponification and hydrolysis reaction initiated upon introducing alkali solution in the modified DEC-HEMC composite. The saponification process involves the hydrolysis or cleavage of ester bonds in the presence of a strong base . Saponification reaction of DEC-HEMC with NaOH initiates the cleavage of the ester bond in DEC by the hydroxide ion from the alkali solution.…”

“…The saponification process involves the hydrolysis or cleavage of ester bonds in the presence of a strong base. 75 Saponification reaction of DEC-HEMC with NaOH initiates the cleavage of the ester bond in DEC by the hydroxide ion from the alkali solution. The hydrolysis reaction exploits the DEC and NaOH.…”

“…The saponification process involves the hydrolysis or cleavage of ester bonds in the presence of a strong base. 75 + +…”

Integração numérica de leis de velocidade diferenciais com o uso do SCILAB

“…21 O sistema de EDO's que resulta do mecanismo formado pelas reações elementares reações 2 e 3 não possuem solução analítica. Dessa forma, utilizaremos esse mecanismo para apresentar a entrada de dados para a resolução pelo método numérico.…”