306 M. Kekule on Fumaric Acid. 



obtain a series of bodies isomeric with the polycthylenic alcohols; 

 the reaction, however, is quite different: the aldehyde dehydrates 

 glycol, and unites with the oxide of ethylene thus formed : — 

 .C 2 H 6 O 2 + G 2 H 4 O=G 4 IPO 2 +H 2 0. 



Glycol. Aldehyde. New body. 



It is a colourless limpid liquid, with an agreeable penetrating 

 odour, resembling that of aldehyde. ' It boils at 82 0, 5. 



If aldehyde is the oxide of ethylidene, the compound is a 

 mixed oxide of ethylene-ethylidene. The body slowly reduces 

 alcoholic solution of nitrate of silver. Heated with acetic acid, it 

 regenerates diacetate of glycol. 



Kekule has published* an interesting communication on fu- 

 maric and some allied organic acids. When malic acid, 

 G 4 H 6 O 5 , is heated, it loses water, and gives two isomeric bodies, 

 fumaric and maleic acids, G 4 H 4 9 4 . 



When fumaric acid is treated with bromine in the presence of 

 water, no action takes place in the cold, but at the temperature 

 of the water-bath the bromine rapidly disappears, and a quantity of 

 perfectly white crystals are obtained, which are dibromosuccinic 

 acid, G 4 H 4 Br 2 4 . The formation of this body is interesting, 

 inasmuch as it takes place by a simple addition of the elements, 

 and not, as is usually the case in the action of bromine on 

 organic substances, by substitution : thus 



€ 4 H 4 O 4 + Br 2 = C 4 H 4 Br 2 O 4 



Fumaric acid. Dibromosuccinic acid. 



Hydrobromic acid also, when heated with fumaric acid, yields some 

 monobromosuccinic acid, but the action is very slow. 



G 4 H 4 O 4 + HBr = C 4 H 5 Br O 4 



Fumaric acid. Monobromosuccinic acid. 



Fumaric acid can also be converted into succinic acid by the 

 action of hydrogen. The experiment succeeds by means of 

 hydriodic acid, but is most easily effected by means of nascent 

 hydrogen. It is simply necessary to add sodium-amalgam to a 

 solution of fumaric acid in water to convert it entirely into suc- 

 cinic acid. 



G 4 H 4 4 + H 2 =G 4 H 6 4 



Fumaric acid. Succinic acid. 



This action of nascent hydrogen is as unusual as that of bro- 

 mine. Hydrogen in the nascent state can reduce organic sub- 

 stances by taking away oxygen ; but there are few cases in which 

 an organic substance unites directly with hydrogen. 



* Liebig's Annalen, Supplement, July 186L 



