XI, A, 2 Brill: Diethylsuccinosuccinate, II 69 



which heads at 1/a=3,300. The similarity of the bands of 

 diethylsuccinosuccinate and of diethyldioxyterephthalate argues 

 for a like cause of the absorption, and it was found that they 

 were both made up of about 90 per cent enol form and 10 per 

 cent keto form. The acetyl derivative of the latter still shows 

 selective absorption, but the bands are shifted, heading at 

 different points and appearing at different concentrations. The 

 absorption curve is very similar to that found for acetyl methyl 

 salicylate by Gibbs and Brill.^^ The constitution of these com- 

 pounds is analogous; consequently one would expect to find the 

 same type of absorption spectra and not have the selective 



COOC2H5 COOC2H5 



H— /^— OOCCH3 H— /^ 



H3CCOO- 



\/ 



-H H— 



I I 



COOC2H5 H 



— OOCCH3 

 — H 



Terephthalate. Salicylate. 



absorption almost destroyed as is the case for the acetyl deriv- 

 ative of diethylsuccinosuccinate. 



Diamidoterephthalic ester gives an absorption curve bearing 

 a slight resemblance to that of the diimide of diethylsuccinosuc- 

 cinate in that both head at 1/A= 2,300, but the former appears 

 at a lower concentration. When a slight excess of two mole- 

 cules of hydrochloric acid is added, the band does not disappear, 

 but is somewhat shifted toward the ultra-violet region, indicat- 

 ing that the free valencies of the nitrogen have not been satu- 

 rated by the acid, but that the acid has been added to form a 

 salt of the same character as that formed by thiophthaloxime ^' 

 with sulphuric acid. 



Baeyer ^^ points out that dihydroterephthalic ester no longer 

 possesses the properties of an aromatic compound, but must be 

 classified as an aliphatic compound. However, it shows selec- 

 tive absorption, although to a less extent than terephthalic ester 

 itself. If one accepts the partial valency theory as announced 

 by Collie and adapted by Pratt ^* to be the explanation of selec- 



" Loc. cit. 



''Pratt and Brill, This Journal, Sec. A (1914), 9, 115. 

 "Ber. d. deutsch. chem. Ges. (1886), 19, 1797; Ann. d. Chem. (1888), 

 245, 103, 



"This Journal, Sec. A (1913), 8, 420. 



