Chemistry. -- -On tJir .s;'i,iji/r.</ /ii/i/nicir/'nu n-itli hr<> i-oiijiiijiitt'il 

 si/sti'iiis of (liinlilc hniids. 1.;{.5. hr.nilrii'iw." By Prof. P. van 

 RnMnri{(;ii and W. van Dohsskn. 



Ill 1S7(S Tii.DKN ') ;ulvanct'<l the liypotliesis tlial the terpeiies might 

 lie (ieri\ati\ ('s of a hydrocarlioii dt' the t'oriiiiihi : 



( 'II, = CH — CH = CH ^ CH =r CH,. 



At the meeting- of the x\ssoe. tVanc. pour i'avaiie. des Seieiieos in 

 Paris 28 Aug. IS78, Franciumont pronounced the same opinion and 

 suggested thai this coniiionnd might, ])erliaps, lie obtained by elinn- 

 iiating of the twd chlorine atoms from acrolein chloride. The efforts 

 made by oiu' of us \. K. many yearsago to prejiare that Iiydrocarbon 

 ill (his luaiiuer did not prove successful. The researches on terpenes 

 which afterwards delinitcly led to the result that, in the case of 

 these substances, we are dealing with i-yclic compounds made the 

 above cited hydrocarbon recede into the background. 



The views of Thiki.e on conjugated systems of double bonds, and 

 the researches originated therefrom, in addition to the studies on the 

 aliphatic terpenes myi'cene i\m\ ocimene, hydrocarbons in which the 

 existence <tf three double-bonds has Ikmmi proved by difi'erent inves- 

 tigators, have again drawn our attention to the 1.3. 5 he.\atriene, 

 because it wduld represent the simjilest hydrocarbon in which occur 

 three double Unkings that also foriii two conjugated systems. 



One of us I'v. R.] lias pointed out previously that one of the 

 iiiellioiU which iiiighl lead to llic de>ired product consists in the 

 action of luelals on 15.4 dichloro-l .5 hexadieni'. 



The invesiigalioii> of (ii!iM:K') have acqiiaiiiled us with the ana- 

 logou> liroiiiiue couipouiid which i> formed by the action of phos- 

 jihoriis iribroiuide on ^. di\ iiiy I l;1_\ col. We have treated this substance, 

 [ii'epared according lo (iniNtii's direclioiis, with metals but have not 

 yet succeeded in |irepai-ing the hydrocaibiui in that way. There was 

 however, aiiollier way still al our disposal lo gain our oliject, namelv, 

 by starting from n. di\ iiiyl glycol and com ertiiig this into a foi'inic ester. 



It is known that the formates of [lolyhydric alcohols, in wliicii occur 

 a ()H-group and a formic aciil-residue connected with two ('-atoms 

 linked together, yield, on heating, unsaturated compounds with eli- 

 mination of carbon dioxide and water. It was now obvious to prepare 

 the monoformate of dixinyl glycol. We endeavoured to do this by 

 heating this glycol with oxalic acid but obtained, mainly, brownisii 



') Journ. cliem. Soc. 1878. p. 80. 



-) Ann. d. Ghim. et d. Phys. [6] 26 (189i) p. 305. 



