Ethylenebromonium ion

The chief reason why ethylenebromonium ion m spite of its strained three membered ring IS more stable than 2 bromoethyl cation is that both carbons and bromine have octets of electrons whereas one carbon has only six electrons m the carbocation... 

With respect to the parent ethylenebromonium ion and expressed as heterolytic bond dissociation energies D (R +—Br"). Data from Staley et al. ( 1977). Calculations (Galland et al., 1990) indicate that this ion is not bridged but open. 

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