( 113 ) 



product melt ing- at 108° — 109°, which he considers to be a geome- 

 trical isomer. On preparing *) the tetrabromide according to Griner the 

 sole product obtained was that melting at 112°, which proved identical 

 with the tetrabromine additive product prepared from the hydro- 

 carbon, as described above. For a mixture of these two bromides 

 exhibited the same raeltingpoint as the two substances separately. 



Prolonged action of bromine on the tetrabromide according to 

 Griner, yielded, finally, the hexabromide melting at 163° — 164', which 

 is identical with the one prepared from the hydrocarbon. 



The bromine derivatives described coupled with the results of 

 Griner prove that our hydrocarbon has indeed the formula given above. 



According to Thiele's views on conjugated double bonds we might 

 have expected from the addition of two atoms of bromine to our 

 hexatriene the formation of a substance with the formula 



CH.Br — CH = CH — CH = CH — CH.Br ... (1) 

 or 



CH,Br — CH = CH — CHBr — CH = CH,. . . (2) 

 from the tirst of which, on subsequent addition of two bromine 

 atoms the following tetrabromide would be formed. 



CH.Br — CHBr — HC = CH — CHBr — CH^Br. . . (3) 



As, however, the dibromide obtained is identical with that prepared 

 from s. divinyl glycol, to which, on account of its mode of formation, 

 w^e must attribute the formula 



CH, == CH - CHBr — CHBr — CH =r CH, . . . (4) 

 (unless, what seems not improbable considering certain facts observed, a 

 bromide of the formula (1) or (2) should have really formed by 

 an intramolecular displacement of atoms) the rule of Thiele would 

 not apply in this case of two conjugated systems. 



Experiments to regenei'ate the gl^^col from the dibromide have 

 not as yet led to satisfactory results, so that the last word in this 

 matter has not yet been said. The investigation, however, is being 

 continued. 



Meanwhile, it seems remarkable that only the first molecule of 

 bromine is readily absorbed by a substance like this hexatriene, which 

 contains the double bond three times. 



By means of the method of Sab.\tier and Senderens, hexatriene 

 may be readily made to combine with 6 atoms of hydrogen. If its 



>) Ann. chim. phys. [6] 26. (1892) 381. 



2) Investigations on a larger scale will have to decide whether an isomer, melt- 

 ing at 108°, really occurs there as a byproduct which then exerts but a very 

 slight influence on the melting point of the other product. 



8 



Proceedings Royal Acad. Amsterdam. Vol. IX. 



