176 



To the product of iliumination of coiimaiiii one of these four 

 structural formulae must be assigned. 



Also another biscoumarin is known, obtained by Knut T. Strom ') 

 bj boiling biscoumaric acid, formed by illumination of coumaric 

 acid, with anhydrous acetic acid. This biscoumarin is, as Strom 

 already communicated, different from the biscoumarin obtained by 

 illumination of coumarin, nor is it identical with the hydrodicou- 

 marin of Fittig and Dyson. 



The biscoumaric acid of Strom is formed from coumaric acid, of 

 which no metastable forms are known till now, in a conformable 

 way as «-truxillic acid of «-normal cinnamic acid, and therefore it 

 is very likely that this biscoumaric acid will have a conformable 

 structure to «-truxillic acid. The properties of this biscoumaric acid 

 known at present are in agreement with this, as will be shown. 



The biscoumarin of Strom would then possess the structual 

 formula I, the coumarin-rings being situated on difFerejit sides of 

 the ring. 



To distinguish the different biscoumaric acids I propose to give 

 to these acids similar names as to the truxillic acids, and then the 

 biscoumaric acid of Strom must be called «-biscoumaric acid, and 

 its biscoumarin «-biscoumarin. The melting- at the same time 

 decomposition-points of the two substances are the same, viz. 

 318° (Strom stated them to be above 275°); «-biscoumaric acid also 

 changes into its biscoumarin when heated to 250°. The biscoumarin 

 obtained by illumination of coumarin might be different from «-bis- 

 coumarin by the position of its coumarin-rings situated, on the 

 same side of the tetramethylene-ring or it might be one of the two 

 other possible biscoumarins indicated by figure II. Tiie first sup- 

 position was not very likely, the two biscoumarins showing no 

 change when heated at 210° with the acetic acid aniiydride, whilst, 

 when they had onl}^ a difference in the situation of the coumarin- 

 rings with respect to the tetramethylene-ring, a change of one into 

 the other was probable. This experiment is, however, not a con- 

 clusive proof of a different binding of the coumarin-molecules in 

 the biscoumarins. The best way to decide this is to prepare the acid 

 of the biscoumarin, converting it lo the dimethylether, and to try if 

 through heating with the acetic acid anhydride at 210° an anhy- 

 dride is formed which gives a dimethylether of another biscoumaric 

 acid. If the two coumarin-rings aie situated on the same side of 

 the tetramethylene ring, no other biscoumaric acid is formed, whilst 



1) Ber. 37, 1383. 



