822 REPORT— 1898. 



symmetric force, therefore — any force, for example, such as comes into play in the 

 motions of the symmetric molecules of a gas or a liquid — which affects one of these 

 hydrogen atoms in one molecule of the compound CHjX'Y', has an equal chance 

 of affecting the other hydrogen atom in another molecule. If the right-hand 

 hydrogen atom in fig. -3 is replaced by the radicle Z', we obtain the enantiomorph 

 represented in fig. I ; if the left-hand hydrogen atom, that represented in fig. 2. 

 The chances in favour of these two events being equal, the ratio, 



Number of occurrences of event I, 



Number of occurrences of event II. 



will, if we are dealing with an infinitely great number of molecules, approximate 

 to unity. AVe therefore obtain a mixture, optically inactiA'e by intermolecular 

 compensation. 



All cases of the conversion of symmetric into asymmetric compounds may be 

 referred to the same category, no matter whether the chemical process is one of 

 substitution or of addition, or whether the resulting molecule contains one or more 

 asymmetric carbon atoms. Thus, in the reduction of a ketone of the formula 

 X'.OO.Y' to a secondary alcohol of the formula X'. C'H(OH).Y' ; in the transforma- 

 tion of an aldehyde by the addition of hydrocyanic acid into a nitrile of an 

 a-hydroxy-acid ; in the oxidation of fumaric acid to racemic acid — cases typifying 

 the various additive processes in which asymmetric groupings are produced — there 

 is one condition common to all : in the symmetric compound, with which we start, 

 there are, in every case, two identical points of attack, equidistant from the plane 

 of symmetry of the molecule, and the result is that the two possible events happen 

 in equal number, so that the mixture of enamiomorphs obtained is optically in- 

 active by compensation. We are, of course, in many cases able afterwards to 

 separate these enantiomorphs by the methods devised by Pasteur, and thus obtain 

 the single opticalh' active compounds ; but we cannot produce them singly as long, 

 as we have at our disposal only the symmetric forces which we command in the 

 laboratory. 



Precisely the same state of things prevails when symmetric molecules unite, 

 under the influence of symmetric forces, to build up an asymmetric crystalline 

 structure. When, for example, sodium chlorate crystallises from its aqueous solu- 

 tion, the number of right-handed crystals is, on the average, as was shown by 

 Kipping and Pope, equal to the number of left-handed ci-ystals. The same fact 

 was proved by Landolt by observing the optical inactivity of the mixture of micro- 

 scopic right and left crystals obtained ))y adding alcohol to a concentrated aqueous 

 solution of sodium chlorate. The two possible asymmetric events occur in equal 

 number. 



Non-living, symmetric forces, therefore, acting on symmetric atoms or mole- 

 cules, cannot produce asymmetry, since the simultaneous production of two oppo- 

 site asymmetric halves is equivalent to the production of a symmetric whole, 

 whether the two asymmetric halves be actually united in the same molecule, as in 

 the case of mesotartaric acid, or whether they exist as sepai-ate molecules, as in the 

 left and right constituents of racemic acid. In every case, the symmetry of the 

 whole is proved by its optical inactivity. 



The result is entirely different, however, when we allow symmetric forces to 

 act under the influence of already existing asymmetric, non-racemoid compounds. 



Thus, if we start with an optically active compound — a compound containing 

 one or more asymmetric carbon atoms and non-racemoid — and, by appropriate 

 chemical reactions, render asymmetric some carbon atom in the compound which 

 was not previously so, then it does not follow that the two forms represented by 

 the two possible arrangements of this new asymmetric carbon atom will be pro- 

 duced in equal quantity. The compound with which we start has no plane of 

 symmetry ; and, although there are still the two possible points of attack, one will 

 be more exposed than the other ; in fact, one mode of attack may so predominate 

 that apparently only one asymmetric compound is formed, the other compound, if 

 formed at all, escaping detection by the smallness of its amount. A case in point 



