The mechanism of Chemical change. —Part III. mutarotation of Aluminium Benzoylcamphor

The study of the metallic-derivatives of benzoylcamphor, as described in a recent paper,* disclosed the existence of mutarotation in freshly prepared solutions of the colourless bivalent beryllium and tervalent aluminium derivatives, but not of the quadrivalent thorium derivative. In the present paper, the detailed investigation of the mutarotation of the beryllium-derivative, as described in the preceding paper of this series, has been extended to the aluminium-derivative, but has led to results of an entirely different character. In particular, whilst the beryllium-derivative appears to undergo mutarotation only in presence of a catalyst, and gives rise to curves which conform to the familiar unimolecular law, the aluminium-derivative has never been obtained in a form in which mutarotation was retarded in the least degree ; and this unpreventable mutarotation is now proved to be of much more complex character, since the rotatory power of the freshly prepared solutions increases with extraordinary rapidity to a strongly marked maximum and then decreases much more slowly to a value which is only a little less than the maximum. Since no solutions could be prepared in which mutarotation was even moderately slow, it was almost impossible to study the effect of catalysis under the same conditions as in solutions of the beryllium-derivative. Attention has therefore been concentrated on the form of the mutarotation curves for an uncatalysed reaction in different solvents. The early experiments of Lowry and Faulknery† showed that the mutarotation did not proceed according to a unimolecular law, but agreed approximately with the formula for a termolecular reaction. The experiments now described have shown that the curves cannot be represented by an equation for a single reaction of the first, second or third order, but conform accurately to an equation of the type [α]t — [α]∞ = Ae - m 1 t + Be - m 2 t .