165 Proceedings of the Royal Irish Academy. 



/3-dibenzyhdene-diacetoresorcinol — is also formed when benzaldehyde is 

 shaken for a few weeks (one month) with a solution of diaeetoresoreinol in 

 dilute, aqueous sodium hydrate. 



An attempt to improve the yield of /3-dibenzylidene-diacetoresoreinol by 

 shaking benzaldehyde and diaeetoresoreinol with dilute alkali for about three 

 months gave a third isomeride, and the latter we have named y-dibenzyli- 

 dene-diacetoresorei noL 



This substance, which melts at 218° C, is nearly white in colour, and 

 crystallizes in equilateral triangles with hexagonal symmetry, thus differing 

 markedly from the other two in melting-point, colour, and crystalline form. 



By heating diaeetoresoreinol and benzaldehyde with alcoholic sodium 

 hydroxide for a short time we obtained orange-yellow prisms, which melted 

 at 204 = C. "We regard this compound, from its appearance, method of pre- 

 paration, and properties, as identical with the a-dibenzylidene-diacetoresor- 

 cinol mentioned above as previously described by Eijkman, Bergenia, and 

 Henrard. 



The method most frequently employed for the preparation of mono- 

 flavanones consists (von Kostanecki, von Lanipe, and Tambor Ber 37 (1904), 

 p. 7S4) of heating an alcoholic solution of a chalkone for several hours with a 

 mineral acid. Owing to the sparing solubility of a-dibenzylidene-diacetore- 

 sorcinol in hot alcohol, we heated a solution of it in glacial acetic acid for a 

 few days with hydrochloric acid, in the hope that it would change to 

 the isomeric diflavanone. The reaction gave, however, as product a bright 

 yellow solid, which crystallized in diamond-shaped plates, and melted at 205 c C. 

 A mixture of it with the parent substance — a-dibenzylidene-diacetoresoreinol 

 — melted much lower than either of the two pure substances. As the 

 properties of the compound indicated that it was not dinavanone, we have 

 named it S-dibenzylidene-diacetoresorcinol. 



The existence of several dibemylidene-diacetoresorcinols may be explained 

 on structural and stereochemical grounds. 



Thus, by the condensation of diaeetoresoreinol (one molecule) with 

 benzaldehyde (two molecules) we may get four structural isomerides, viz. 

 dihydroxy-dichalkone (i), dinavanone (n), hydroxy-chalkone-flavanone (m), 

 and hydroxy-aceto-benzylidene-flavanone (iv). 



| 1 » n | 65 



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