Double Bond Formation by Spontaneous Deactivation

When living polystyrene anion is kept for very long periods or heated to temperatures around 60 °C, a color change occurs. This is due to the elimination of sodium hydride from the active sites leading to the formation of a double bond 37 K However, this 

Recently, the stability of living poly-p-bromostyrene was investigated by Jagur 3S) who postulated a radical mechanism to account for the observed phenomena. Here again terminal double bonds are formed, KBr being eliminated  

However, as in the preceding case, the hydrogen (both allylic and benzylic) in P-position with respect to the carbanionic site is acidic and metalation occurs readily at the expense of another living polymer molecule. Therefore, the fraction of the macromolecules bearing active carbon-carbon double bonds at a chain end is 0.5. 

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