Chemistry. — ''Tivo Crystallised, Isomeric d- Fructose- Penta- 

 aeetates". By Prof. Dr. ¥. M. Jaeger. 



(Communicated in the meeting of June 30, 1917.) 



§ 1. Nine years ago ') the cryslallonomical character was described 

 of a d-Fructose-tetra-acetate (rupt:132° C), prepared by Dr. D. H. 

 Brauns. The compound is monoclinic-sphenoidical, with the parameters: 

 a: 6:^ = 1,3463:1:1,5733, and i? = 52°12'. A short time ago Hudson 

 and Brauns') succeeded in obtaining two isomeric crystallised 

 d-Fructose-penta-acetates, whose form-analogy is strikingly evident, 

 as will be clear from what follows. 



Both penta-acetates possess the same cycle of atoms in their 

 molecules, as is proved by the fact that they both are obtainable 

 from d-Fructose-tetra-acetate, namely the 

 «-modification by means of ZnCl, and 

 acetic acid-anhydride, the /^-modification 

 by means of strong sulphuric acid and 

 acetic-acid-anhydride. 



^ 2. I. «-fZ-FRUCTOSE-PENTA-ACETATE. 



The substance melts at 70° C; its 

 specific rotation at 20° C. is : \a]D = 

 — _}_ 34°, 75 in chloroform-solution. Its 

 taste is a little bitter, and it crystallises 

 from a mixture of alcohol and chloroform 

 in prismatic crystals which are repro- 

 duced in fig. 1. 



Rhomhic-bisphenoidical. 

 a:b:c = 0,4946 : 1 : 0,3349 



Fomis observed: ?>i = |110|, predomi- 



*• 



Fig. 1. 

 (Z-Fruclose-penta-acetate. 



nant, and h — {OlOj, appreciably smaller. The prism-zone shows 

 often disturbances, and its angular values may oscillate within 

 rather wide limits. Furthermore: q — \^\X\, laige and lustrous; 

 tü=:{llli, small and lustrous; 5 = }021|, smaller and someAvhat 

 duller. The external form is elongated parallel the c-axis. 



1) F. M. Jaeger. Proceed. Kon. Acad. Amsterdam, 10. 563. (1908); Zeits. f. 

 Kryst. u Miner. 45. 539 il908). 



2) G. S. Hudson and D. H. Brauns, Journ. Amer. Ghem. Soc. 37. 1283, 2736. (191 B). 



