Manchester Memoirs, Vol. Ixiv. (1920), No. 4 



CH 2 = CH— CH 2 



:Br::::::::H Br 



+ : 



+ C H 2 ;; ;;;;;;; C H C H< 



— + :: 



•Br:::::::::H 7 Br 



/ 



CH^CH— CH. 



Br 



H 

 (I) 



Br 



In the above scheme, the attack of the free partial valency of 

 the hydrogen of hydrobromic acid on the bromine of allyl 

 bromide induces a conjugation resulting in the appearance of 

 a positive partial valency at the other end of the chain. Ring 

 formation follows* and the orienting effect is secured since the 

 bromine is already partly attached to the position which it 

 ultimately retains in trimethylene bromide. The further 

 rearrangements may be conceived in the following manner : 



CH9....CH....CH. 



CHp— CH— CH. 



1 



Br H 



Br 



Br 



H Br 



= BrCrVCH 2 -CH 2 Br 



On the other hand one of the hydrogen atoms of allyl bromide 

 might be attacked by the bromine of hydrobromic acid and 

 this leads to a different result as shown below : — 



CH 2 =CH CH Br CH~ CH~r CH Br 



H 



Br H 



H 



Br. 



+ 



H 



+ 



+ 



CH 9 =CH---CH Br CH,— "CH"— CH Br 



H 



Br H 



H 



Br H 



CH, CH CH Bi 



H 



= CH, -CH Br -CH 2 Br 



Br H 



