1903.] on Recent Advances in Stereochemistry. 309 



substance d-B, d-A — its solubility, melting point, etc. — will be 

 conditioned by an enantiomorphous relationship of quite a different 

 order from that determining the corresponding properties of the salt 

 1-B, d-A ; the solubilities, being determined by different factors, will 

 naturally also differ, and the two salts will therefore be separable by 

 crystallisation. The first resolution of a compensated base was 

 effected by Ladenburg in 1885 and consisted in resolving the syn- 

 thetic alkaloid coniine into its optically active components — one of 

 which proved to be identical with the alkaloid contained in the 

 juice of the hemlock — by crystallising it with d-tartaric acid. Since 

 this date the methods of resolving compensated bases have been 

 materially improved by the application of optically active acids 

 derived from camphor for use in place of the dextro-tartaric acid, 

 and an experiment in illustration can now be shown on the lecture 

 table. On adding a solution of ammonium dextro-bromocamphor- 

 sulphonate to a solution of compensated tetrahydro-/5-naphthylamine 

 hydrochloride, a white crystalline precipitate of d-tetrahydro-y8- 

 naphthylamine d-bromocamphorsulphonate, — the salt d-B, d-A, — 

 is thrown down, whilst the laevo-tetrahydronaphthylamine remains 

 in the solution as its hydrochloride. The resolution in this, and in 

 many other cases, can thus be very rapidly effected, and by still 

 further applying the optically active camphorsulphonic acids a con- 

 siderable extension of the original van't Hoff-Le Bel theory has 

 become possible. These workers traced all cases of optical activity 

 to the presence of an asymmetric carbon atom and deduced from 

 their work the conclusion that the environment of the carbon atom 

 in methane is a tetrahedral one. It is true that all the optically 

 active substances which have yet been obtained from natural sources 

 owe their optical activity to the presence of an asymmetric carbon 

 atom, but it is important to note that by applying the second Pasteur 

 method to the investigation of synthetic materials, compounds owing 

 optical activity to the presence of asymmetric atoms other than those 

 of carbon can be prepared. 



Thus, ammonium iodide has the molecular composition NH4I 

 and, like methane, contains in its molecule four hydrogen atoms, 

 which are replaceable by other atoms or groups of atoms ; on replac- 

 ing these hydrogen atoms by the four groups of atoms or radicles, 

 methyl, allyl, phenyl, and benzyl, a substance is obtained which is 

 conveniently named methylallylbenzylphenylammonium iodide and 

 has the following constitution — 



CH3 t'gHj 



\ / 



N 



C3H, I C,H. 

 I 



On replacing the iodine atom in this molecule by an optically 

 active group of atoms, viz. by the dextrobromocamphorsulphonic 



