273 



and the same is true for the sodium-*;i\\ of dextrogyratory at-nitm- 

 camphor; laevogyrntc glycerinic acid gives a dextrogyrate calcium- 

 >alt '). The chlorohydrate of dextrogyrate x-nmino succinic acid is 

 laevogyratory 2 ) ; and the opposite rotations of the derivatives of 

 uspartic acid are well-known, according to the event that the H of 

 of the COOH-group be replaced by metal-atoms, or that a salt 

 formed by addition of an acid to the ammo-group 3 ). In these 

 cases the circumstances during the chemical process are such as 

 to make a re-arrangement of the original molecule highly im- 

 probable, because with a few precautions each change of temperature 

 may be avoided. The problem of explaining .the change of sign 

 of the rotatory effect after substitution, cannot be solved at present, 

 as we are still waiting for a sufficient dynamical explanation of the 

 molecular rotatory power in its dependence on the dissymmetrical 

 arrangement of the atoms in the molecule. Here lies a problem 

 of the highest interest and urgency for mathematical physicists, 

 and it is to be hoped that some advance will be made in this 

 difficult matter within not too remote future. 



3. In this connection we have however to consider a pheno- 

 menon which is also of high importance for the problems with 

 which we shall have to deal further-on in this chapter. I mean 

 the remarkable inversion discovered by W a 1 d e n 4 ) in 1 896, and 

 which may best be elucidated by some examples. 



If in /aeyogyratory malic acid, the hydroxyl-group be replaced 

 by chlorine, a dextrogyratory chloro-succinic acid results. This in 

 itself is not particularly remarkable, because in accordance with 

 what has been said above, both substances can have analogous 

 configurations in space, notwithstanding their opposite rotations. 

 But if this chloro-succinic acid is transformed into malic acid again, 

 the last appears to be this time the dextrogyratory antipode. In 

 this process there must have occurred at least one inversion, as 

 the dextro- and laevogyratory malic acids have certainly enan- 

 tiomorphous configurations. It is however questionable whether 

 the inversion took place during the change of the malic acid into 





1) E. Fischer and W. A. Jacobs, Ber. d. d. Chem. Ges. 40. 1068. (1907). 



2) E. Fischer and K. Raske, Ber. d. d. Chem. Ges. 40. 1053. (1907). 



3) V. Meyer and P. Jacobson, Lehrb. d. Organ. Chemie, 2e Aufl. /, 2. 778, 

 779, (1913). 



4) P. Walden, Ber. d. d. Chem. Ges. 29. 133. (1896); 80. 2795, 3146. (1897); 

 82. 1833, 1855. (1899); 40. 2470. (1907); etc. 



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