Ryan and Plunkett — On Unsaturated /3-Diketones. — III. 201 



3.4-dimethoxy-cinnamoyl-pyruvate (II), and 3.4-dimethoxycinnamoyl-pyruvic 

 acid (III) : 



_0CH 3 

 .CO . CH : CH-/ VoH 



CH 2 



^CO 



I 

 . CH : CH-/ 



VoH 



~OCH 3 



_OCH 3 



,co . 



CH 2 



CH : CH-/ 



ii 



VoCH : 



NjO . 



CO • OCHs 



_OCH 3 



.CO 

 CH 2 



. CH : CH-/ 



in 



VOCH; 



N ^co 



. COOH 





and bear in mind that since the auxochromic effect of the hydroxyls in the 

 vanillin residues of curcumin can only be very slight, the curcumin shades 

 should not differ materially from those of its dimethyl ether, it is evident 

 that the three compounds should give similar shades to mordanted wool. 

 The same double chromophore, -CO : CH : CH-, is present in all the com- 

 pounds, and also the auxochrome is the acidic methylene radical. In the cur- 

 cumin molecule the double chromophore occurs twice, but this is to some extent 

 balanced by the fact that the methylene radical in X . CO . CH 2 . CO . COOR 

 is a much stronger auxochrome than the same radical in the group 

 X . CO . CH, . CO . X. Still more is this so in the case of the pyruvic acid, 

 the shades of which are even more intense than those of curcumin. 



It will be seen also that the tints got with cinnamoyl-acetylmethane are 

 slightly less intense than those got with cinnamoylbenzoyl-methane, and this 

 is probably due rather to the greater intensification of the auxochromic 

 methylene radical by the more acidic benzoyl radical than to the slight 

 chromophoric character of the phenyl group. This view gains support from 

 the intensification of the shades obtained by replacing phenyl by the still 

 more acidic carboxyl radical. 



The effect of methoxyl in increasing the depth of the colour is shown by 

 a comparison of the tints got with cinnamoyl-pyruvic acid, p. methoxy- 

 cinnamoyl-pyruvic acid, and 3 - 4-dimethoxycinnamoyl-pyruvic acid, the last 

 compound dyeing mordanted wool deeper shades than any other member of 

 the group. 



[2<?2] 



