ON ABSORPTION SPECTRA AND CHEMICAL CONSTITUTION, 211 



agreement with the views now generally held as to their relationship with 

 one another. But, as already observed, the absence of selective absorp- 

 tion is not in harmony with the constitution of cyanuric acid when it is 

 represented by a formula so closely analogous to that of pyridine and 

 still more closely to that of dimethylpyrazine. On this account it may 

 fairly be considered as very doubtful whether the constitution of cyanuric 

 acid is rightly understood. 



The Absorption S-pectraqf Dihenzoyl Methane and a-Oxyhenzalacetophenone. 



These two substances are related to each other in the same manner 

 as Knorr's dibenzoyl succinicesters examined by Hartley and Dobbie.' 

 Their constitution is represented by the following formulae : — 



CeH^.CO CeHj.CO 



I I 



CHo CH 



CgHj.CO CgHg.COH 



Dibenzoylmethane a-Oxybenzalacetophenone 



m.p. 77-78° m.p. 77-78° 



(o-Hydroxybec zy lidene acetophenone) 



The enolic form is, in this case, the more stable of the two, the keto 

 form in solution passing rapidly into the enolic form on the addition of an 

 acid. It is the reverse with the dibenzoylsuccinic esters ; the enolic ester 

 passes into the keto form spontaneously. 



As the study of cases of this kind is of particular interest, and but 

 few liave been examined, Miss Alice E. Smith, B.Sc, of the University 

 College of North Wales, Bangor, kindly undertook, at the request of the 

 committee, to investigate the absorption spectra of these substances. 

 Mr. R. D. Abell, B.Sc, 1851 Exhibition Scholar of the University 

 College of North Wales, Bangor, was good enough to supply pure 

 specimens of these substances for examination. 



Dibenzoylmethane (CuH5.CO.CH2.CO.CgHg). — The preparation of 

 dibenzoylmethane may be divided into the following stages : — 



(1) The preparation of benzalacetophenone from benzaldehyde and 

 acetophenone.^ 



(2) Preparation of dibrombenzalacetophenone from benzalaceto- 

 phenone.^ 



(3) Preparation of monobrombenzalacetophenone from dibrombenzal- 

 acetophenone."* 



(4) Preparation of dibenzoylmethane from monobrombenzalaceto- 

 phenone. 



a-oxyhenzalacelophenone (C^Hg.CO.CH :C(0H).CgH5) (or a-Hydroxy- 

 benzylidene acetophenone). — This substance was prepared by Baeyer and 

 Perkin by heating dibenzoylacetic ester with water.^ The method of 

 acting with sodium ethoxide or metallic sodium on a mixture of ethyl 

 benzoate and acetophenone employed in the present case has been de- 

 scribed by Claisen.^ 



' Trans. Chem. Soc, 1900, 77, 498^ 

 * Ber., 20, GG5 ; 14, 2iC4: ; 29, 1492. =^mw., 308, ,^23. 



' Ann., 308, 22(j. ^ Ber., 16, 2134 ; Chem. Soc. Trans., 47, 250. 



" Ber., 20, 655 ; Ann., 291, 52. 



p2 



