DOUBLE LINKED STEREO-ISOMERS 123 



same acid is the stronger, as might be expected from the 

 influence exerted by the oxygen of either carboxyl on the 

 other carboxyl group, which is close to it. The dissociation 

 constants, which are closely related to the strength of an 

 acid (Part I, p. 137), are respectively 1 



KMal. = T'I7, Kpum. = '93- 



Thirdly, the acid salt of maleic acid is weaker than that 

 of fumaric 2 , just because in the ions of these salts, 



HCCOO HCCOO 

 HCCOOH COOHCH 



the negative charge opposes further dissociation, and does so 

 more strongly in maleic acid, as being nearer. The quantity 

 dissociated, found by means of the rate of inversion, is 



v Diss. Maleic Acid Diss. Fumaric Acid 

 6 4 0-342 % 0-932 % 



I2 8 0-55 1.52 



256 0-918 2.74 ,, 



Finally the above formulae are confirmed by the results 

 of oxydation in aqueous solution. Permanganate gives 

 with maleic acid, on taking up hydroxyl, inactive undecom- 

 posable tartaric acid, as is to be expected : 



OH 



HCCOOH 

 gives TTppnnTT 

 HCCOOH 



OH 



whilst fumaric acid gives, under the same circumstances, 

 racemic acid : 



HCCOOH COOHCH 



II or || 



COOHCH HCCOOH 

 gives 



OH OH 



HCCOOH COOHCH 



COOHCH HCCOOH 



OH OH 



1 Zeitschr.f. Phys. Chem. 3. 380. 2 1. c. 25. 241. 



