Chemistry. — "A crystallized compound of isoprene with sulphur 

 dioxide". By Mr. G. de Bruin. (^Communicated by Prof. P. van 

 Romburgh). 



(Gomraunicated in the meeting of June 27, 1914). 



As is known from the patent literature^) unsaturated liydrocarbons 

 with conjugated double bonds combine in different circumstances 

 with sulphurous acid. Thus, crude isoprene on shaking with an 

 aqueous solution of that acid yields a compound sepai-ating in the 

 form of white flakes. 



When I mixed isoprene, prepared according to Harries's method -) 

 (from carvene) and which had been purified by fractionation, the 

 fraction from 34° to 38° being collected separately, with an equal 

 volume of liquefied sulphur dioxide and left this mixture in a sealed 

 tube at the temperature of the room, I obtained after one or two 

 days a considerable quantity of a crystallized product. As a rule the 

 mixture soon turns brown, but sometimes it remains colourless. 



Beside the crystals is always formed a viscous, white mass which 

 on drying gets hard and brittle. In some experiments no crystals 

 were deposited, but on pouring the contents of these tubes into a 

 small flask it instantly solidified owing to the formation of a large 

 number of crystals. 



The crystalline product may be readily recrystallized from ether. 

 By repeating this operation a few times a pure, white product is 

 obtained melting without decomposition at 62°. 5. Presence of moisture 

 is not necessary for the formation of the crystals, anyhow exactly 

 the same result was obtained with tubes filled with sulphur dioxide 

 dried over sulphuric acid, and dry isopiene. 



The analysis gave the following results : 



0.2016 grm. of the substance (burnt in a close tube with lead 

 chromate) gave: 0.3384 grm. CO^ and 0.1107 grm. H,0 



0.1612 grm. of the substance gave 0.2814 grm. BaSO, 



0.1779 „ „ „ „ „ 0.3156 „ 



Found : 45.77 »/„ C. 6.10 «/„ H. I. 23.97 % S. II. 24.35 % S. 



Theory for C,H3S0, : 45.46 »/„ C. 6.06 »/„ H. 24.29 »/„ S. 



Determination of the molecular weight by means of tiie lowering 

 of the freezing point in benzene: 5491 grm. of substance in 

 23.806 grms. of benzene gave a lowering of 0°.835. Molecular 

 weight found: 138. 



M D. Pat. B. 59862, kl. 120, Gr. 2, 18 Aug. 1910. 

 2) Ann. 383, 228 (1911). 



