Structures of Ethylene Oxide and Cyclopropane

Abstract

THE recent communication of Walsh¹ includes several statements which are open to question. The suggestion that the reactions of ethylene oxide are at present considered to be due to instability caused by ring-strain is not acceptable without qualification and explanation. Nobody, one hopes, still retains any purely mechanical idea of strain such as one finds in the springs of models. Nowadays reactions are universally attributed to the functions of electrons and. nuclei, and an interpretation of the special reactivity of such a series as acetylene, ethylene, cyclopropane and cyclopentane can surely be found by the application of quantum mechanical principles to the usual formulæ. These represent nothing more than the mode of linking of the atoms in the molecule, combined with an indication of the degree of symmetry of the statistical distribution of electrons. Thus we may be confident that the ring-binding in cyclopropane has the symmetry of an equilateral triangle, that in ethylene oxide of an isosceles triangle, and that of propylene oxide of a scalene triangle. The usual formula for cyclopropane is therefore as satisfactory a symbol as can be devised.