49i Scientific Intelligence. 



Tafel obtained some time ago, two sugar derivatives in the form 

 of their osazones, produced by precipitating with phenyl-diamide, 

 which they called ct-acrosazone and /3-acrosazone respectively. The 

 former these chemists have now further examined. By the action 

 of hot concentrated hydrogen chloride, the ^-acrosazone dissolves 

 to a clear dark red liquid which on cooling deposits crystals of 

 phenyl-diamide hydrochloride. The mother liquor is diluted, 

 neutralized with lead carbonate, decolorized and precipitated with 

 barium hydrate. The precipitate contains the a'-acrosone, having 

 the formula CH 2 . OH . (CHOH) s CO . COH ; which is an oxidation 

 product of a simple sugar. The lead compound was decomposed 

 with sulphuric acid, treated with barium carbonate, decolorized 

 and evaporated to a syrup, which in the cold solidified to an amor- 

 phous mass. By warming the dilute solution of a-acrosone with 

 zinc dust and acetic acid, it was reduced readily ; and after re- 

 moving the zinc by hydrogen sulphide, evaporation and extrac- 

 tion with absolute alcohol, ether produced a precipitate of the 

 new sugar ar-acrose in colorless flocks which soon deliquesced to a 

 syrup. This substance shows the closest analogy with the glu- 

 coses. It tastes sweet, reduces Fehling's solution, and ferments 

 with yeast. Moreover on reduction with sodium amalgam it 

 yields a substance closely resembling mannite which the authors 

 call acrite. Both acrose and acrite, however, are optically inac- 

 tive; and this is the only respect apparently in which the former 

 differs from the glucoses or the latter from mannite. — Ber. JBerl. 

 Chem. Ges., xxii, 97, January, 1889. G. f. b. 



4. On Geometrical Isomerism. — Wislicenus and Holz have 

 described a striking instance of geometrical isomerism in the case 

 of the dibromide of crotonylene. In this form of isomerism, the 

 compounds are precisely similar in their constitution and differ 

 only in the relative positions of their atoms in space. By the di- 

 rect action of bromine upon crotonylene CH 3 . C j C . CH S , a dibro- 

 mide CII 3 . CBr : CBr. CH 3 is formed the atoms of which as the 



CH 3 . C . Br 

 authors show, are arranged in space thus : || the two 



CH 3 .C.Br 

 similar groups being symmetrical with respect to an assumed 

 plane between them. If, however, a dibromide be formed either 

 by removing from crotonylene tetrabromide two of its bromine 

 atoms, or by withdrawing from one of the tribrombutanes 

 CH 3 . CHBr. CBr 2 . CH S a molecule of hydrogen bromide, the new 

 dibromide is found to be quite a different substance from the first. 

 While it has necessarily the same empirical formula, its boiling 

 point was found to be about 3° higher than the other dibromide 

 and it behaved quite differently on reduction with zinc dust. The 

 authors can explain these differences only on the assumption that 

 the arrangement of its atoms in space is centro-symmetrical 

 CH 3 . C . Br 



|| ; and they give the name isocrotylene dibromide to 



Br.C.CH. 



