viii, a, 6 Pratt: Phthalides and Related Compounds 401 



PHTHALIC ANHYDRIDE 

 C=0 



C 6 H 4 <( ^0 



c=o 



The absorption spectrum of phthalic anhydride was studied 

 in glacial acetic acid solution to avoid any possibility of dis- 

 rupting the lactone ring. It shows a small band heading at 



T = 3440, very similar in outline and persistence to that given 



by phthalic acid, but less refrangible (fig. 2). This solution is 

 not fluorescent to a noticeable degree. 



The anhydride in sulphuric acid fluoresces purple under the 

 arc, and gives an absorption spectrum identical with that of 

 phthalic acid in the same solvent. 



MALEIC ANHYDRIDE 



HC-C=0 



I > 



HC-C=0 , 



The anhydride was prepared from malic acid according to 

 directions given by van der Riet 1 and recrystallized from ether 

 and from chloroform until pure. The solution in glacial acetic 

 acid shows a band of very slight persistence heading at about 



^ =3400 (fig. 3). 



The solution in sulphuric acid shows even less selective ab- 

 sorption, with a step-off at about ~ = 3500 to 3900. 



A 

 PHTHALIDE 



C=H 2 



c 6 h/ ^>o 

 c=o 



Phthalide was made both by reducing phthalyl chloride 2 and 

 from phthalimide. 8 Both products were purified by repeated 

 boiling with bone black and recrystallization from water. This 

 was necessary to remove traces of resinous impurities that give 



1 Ann. d. Chem. (Liebig) (1894), 280, 216. 



1 Ber. d. deutsch. chem. Ges. (1877), 10, pt. 2, 1445. 



•Graebe, Ann. d. Chem. (Liebig) (1888), 247, 291. 



