Croatica Chemica Acta, Vol. 78 No. 1, 2005.
Short communication, Note
Mechanism of Ferrocenylmethyl Benzoate Formolysis and Acetolysis
Biserka Cetina-Čizmek
Snježana Vodopija Mandić
Smiljko Ašperger
Abstract
The formolysis and acetolysis of ferrocenylmethyl benzoate are proton catalyzed and accelerated by addition of perchloric acid. Our earlier experiments have shown that at a temperature of about 20 °C addition of a common benzoate ion in formolysis of 3.2 x 10–4 mol dm–3 ferrocenylmethyl benzoate suppresses the formolysis rate only slightly but the formolysis is significantly slower at 40 °C. Such rate lowering is not observed in acetolysis of the same substrate. Decrease of the formolysis rate at increased temperatures (20–40 °C) is most probably caused by the decrease of the hydrogen ion concentration, because the stronger formic acid displaces the weaker benzoic acid from sodium benzoate, thus reducing the formic acid concentration in this acid-catalyzed system. This, however, does not occur in the weaker acetic acid. Besides, the acetolysis rates are equal in the presence of 0.1 and 0.2 mol dm–3 sodium benzoate, while the formolysis rates decrease with the addition of benzoate. The strong temperature dependence of the formolysis rates is probably connected with the formation of formic acid dimers and the temperature dependent hydrogen bonding. Hydrogen bonding and the dimer formation in acetic acid are less pronounced than in formic acid.
Keywords
ferrocenyl esters solvolyses; acid catalyzed solvolyses; formolysis and acetolysis; ferrocenylmethyl benzoate; solvent separated ion pairs
Hrčak ID:
2801
URI
Publication date:
24.3.2005.
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