Conjugated Hydrohalogenation (1,2 vs 1,4 addition) Video Lessons

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Problem: What are the expected kinetic and thermodynamic products from the addition of one mole of Br2 to the following dienes?

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For this problem, we have to draw the kinetic and thermodynamic products of the reaction below


  • These reactions will proceed to a conjugated hydrohalogenation which is known to produce multiple products
  • This will follow a simple hydrohalogenation mechanism except we have a possible conjugation which stabilizes the resonance structure


Recall that alkenes are converted to alkyl halides via hydrohalogenation, which occurs in two steps:

(1) protonation – the alkene is protonated, forming a carbocation intermediate and a halide ion. This follows Markovnikov’s rule, which states that the more stable carbocation is formed.


Also, since a carbocation is formed during the reaction, the carbocation may rearrange into a more stable one.


(2) nucleophilic attack – the halide ion comes in and attacks the positively-charged carbon. The stereochemistry for this reaction is unknown since the nucleophile can attack either side of the empty p-orbital.


However, we have 2 consecutive double bonds which make this a conjugated hydrohalogenation. 


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What are the expected kinetic and thermodynamic products from the addition of one mole of Br2 to the following dienes?


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