1. Systematic speculations on the mechanism of chemical reactions were first started by F. London (1928) and by H. Eyring and M. Polanyi (1931). The simplified theory of âionogenic reactionsâ used in the text was first suggested by Ogg and Polanyi (Trans. Far. Soc., 31, 607; 1935) and later elaborated by M. G. Evans and Polanyi (Trans. Far. Soc., 34, 11; 1938).
2. Compare Evans, M. G., and Warhurst, E., Trans. Far. Soc., 35 593 (1939).
3. Brockway, L. O., Beach, J. V., and Pauling, L., J. Amer. Chem. Soc., 57, 2693 (1935).
4. Such a possibility was first considered by M. G. Evans and E. Warhurst for the case of the diene-synthesis (Trans. Far. Soc., 34, 614; 1938) then applied to the present problem by M. G. Evans and M. Polanyi (NATURE, 148, 436; 1941).
5. Rossini, F. D., Bull. Bur. Standards J. Research, 13, 29, 189 (1934). Knowlton, J. W., and Rossini, F. D., ibid., 22, 115 (1939).