1091 



2. a tetrabromide CsHJir, also already descrilx'd bv Ghinkk of 

 the formula CH,=CH-CHBr-CHHr-OHBr-CH,Hr. 



3. a liexabromide CflHj,Br„ liaxijig llio foi-iuiila of a 1 : 2 : 13 :4r : 5 -. (i 

 liexabromoliexaue. 



Adilition of 6 atoms of hydrogen by the Sabatier and Sendeuens 

 method gave normal hexane. 



AI<lioni>;h it was thus shown \yith certainty that by the process 

 employed the desired unsaturated hydrocarbon was obtained, there 

 remained some doubt as to its absolute purity, for instance, because the 

 physical constants of tiie different preparations did not (juito agree. 

 1 1 was, tlierefore, desirable to make efforts to get at a method that 

 could yield this compound, sc important from a tlieoretical point of 

 view, ill a perfectly pure condition. After many tedious experiments 

 we have at last succeeded. 



First of all we tried to gain our object by modifications in the 

 old method; after many experiments the following modus operandi 

 was found to give the best results. 



s-divinylglycol is heated with an equal weight of 99°;, formic 

 acid for half an hour at 105°, the excess of acid is then distilled 

 off in vacuo at 60° and the mixture of formates is decomposed 

 rapidly by heating at the ordinary pressure at 160° — 220°. The 

 upper layer of the distillate is washed with water and distilled in 

 an atmosphere of carbon dioxide or hydrogen, so as to avoid oxida- 

 tion, up to 110° and the liquid obtained is dried over fused calcium 

 chloride. Owing to the modifications introduced the yield of hydro- 

 carbon is considerably larger and amounts to 407o of the glycol 

 used. 



A careful fractionate distillation of the hydrocarbon obtained did 

 not, however, give even now a product with a constant boiling and 

 melting point. 



Experiments made to purify the preparation by freezing, although 

 rising the initial fusion range^) could not be continued as the quantity 

 at disposal was not sufficient. Hence, another method of preparing 

 had to be looked for. 



It was to be expected Ihat by the action of dehydrating agents 

 on hexadiene 1.5-ol 1.4 the desired hydrocarbon might form. This 

 alcohol, obtained by Mr. Le Heux'^) according to F'ouhnieu's method, 

 was treated with potassium pyrosnlphate or phthalic anhydride. 

 From 80 grams of the alcohol could be obtained by heating with 

 5 — 10 grams of potassium pyuosulphate 24 grams, and by heating 



1) The initial fusion traject was — 55° to — 47^.5, the final — 47°.5 to— 33°. 



2) This Proceedings, Febr. 1913, p. 1184. 



