Mécanisme de l'alcoolyse des esters‐I Alcoolyse des propionates et acrylates de méthyle et de butyle normal, en milieu acide

Summary. ‐ It is shown that the acid‐catalysed esterification of propionic and acrylic acids, by absolute methanol, has a frequency factor which is approximately the same in both cases, and for a given temperature, the rate constants depend on the activation energies only, propionic acid: Ea=10,0 Kcal/mole log PZ=6,1 (16) acrylic acid: Ea=12,4 Kcal/mole log PZ=6,2 The same observation is true for another bimolecular reaction i.e. the acid‐catalysed hydrolysis of ethyl propionate and acrylate. ethyl propionate: Ea=16,2 Kcal/mole log PZ=7,5(17) ethyl acrylate: Ea=18,1 Kcal/mole log PZ=7,4. An analogous result is obtained for the acid‐catalysed methanolysis of n‐butyl propionate and acrylate, on the one hand and the acid‐catalysed butanolysis of methyl propionate and acrylate, on the other hand. Methanolysis: n‐butyl propionate: Ea=12,7 Kcal/mole log PZ=4,4 n‐butyl acrylate: Ea=14,4 Kcal/mole log PZ=4,7. Butanolysis: methyl propionate: Ea=12,6 Kcal/mole log PZ=4,3 methyl acrylate: Ea=14,2 Kcal/mole log PZ=4,5. The interpretation of the relative values obtained for the activation energies in these alcoholysis reactions is only possible on the basis of a bimolecular mechanism. Copyright © 1952 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim

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