Structure of Simpler Organic Compounds. 135 



When allyl iodide, CH 2 : CH CH 2 I (the iodine deriva- 

 tive corresponding to allyl alcohol, see p. 78), is treated 

 with sodium, it yields a hydrocarbon with six carbon 

 atoms containing two double bonds 



CH 2 : CH CH 2 I + Na 2 + CH, : CH CH 2 I 



= 2NaI + CH 2 : CH-CH 2 CH 2 CH : CH 2 



By virtue of the two double bonds, the diallyl thus pre- 

 pared will form with bromine a tetrabrom addition product, 

 CH 2 Br - CHBr - CH 2 - CH 2 . CHBr CH 2 Br, from which, on 

 treatment with alcoholic sodium hydroxide, the bromine 

 can be eliminated to yield a substance isomeric with 

 benzene and known as dipropargyl 



CHiBrCHBr.CH2-CH2.CHBr.CH3r + 4KOH = 4KBr + 41^0 

 + CH;C.CH 2 -CH 2 -C:CH 



This substance, boiling point 85, behaves as an unsatu- 

 rated compound should be expected to. It readily forms 

 addition products with bromine, it is readily destroyed by 

 oxidizing agents such as nitric acid, and it forms silver 

 and copper compounds like acetylene (p. 61). In all 

 these respects its behaviour is in marked contrast to the 

 isomeric benzene, boiling point 80 '5, which does not 

 readily form addition products, but substitution products 

 with halogens such as C 6 H 5 Br, and which, on treatment 

 with nitric acid, is not oxidized into compounds with 

 smaller number of carbon atoms, but gives nitro-substitu- 

 tion products such as C 6 H 5 (NO 2 ). Other hydrocarbon 

 derivatives, furthermore, are known, several of which can 

 be isolated from coal tar, which, as regards behaviour 

 towards bromine and nitric acid, behave in a similar way 

 to benzene, yielding bromo- and nitro-substitution products. 

 These can be obtained synthetically from benzene, and are 

 now known to be alkyl substitution products of benzene 



