Addition Of Bromine To Buta

     
The question says:By showing the mechanism of addition, suggest an explanation for why the addition of 1 mol of Br2 lớn buta-1,2-diene forms 1,4-dibromobuta-2-ene rather than 1,2-dibromobuta-3-eneI understand that the non polar Br-Br molecule nears the double bond, and that the Pi electrons in the double bond induce a dipole in the Br-Br molecule with the positive end ending up with the hydrocarbon, whilst a carbocation is formed, which then the other Br joins onto.I'm a bit stuck explaining this with 2 double bonds; which one breaks first? Then how does the carbocation work with there still being a double bond? Lastly, how vị you show that is it 1,4-dibromobuta-2-ene formed?


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The question says:By showing the mechanism of addition, suggest an explanation for why the addition of 1 mol of Br2 to buta-1,2-diene forms 1,4-dibromobuta-2-ene rather than 1,2-dibromobuta-3-eneI understand that the non polar Br-Br molecule nears the double bond, và that the Pi electrons in the double bond induce a dipole in the Br-Br molecule with the positive kết thúc ending up with the hydrocarbon, whilst a carbocation is formed, which then the other Br joins onto.I'm a bit stuck explaining this with 2 double bonds; which one breaks first? Then how does the carbocation work with there still being a double bond? Lastly, how vày you show that is it 1,4-dibromobuta-2-ene formed?
I think you mean buta-1,3-dieneIt doesn't matter which double bond opens first (as they are indistguishable). A Br will bond khổng lồ the kết thúc carbon and you will form the senangngucnoisoi.vnndary carbocation.So far so good.I would then expect the other bromine khổng lồ go lớn the 2 position, leaving the other double bond where it is and forming 1,2-dibromobut-3-ene.If it doesn't, you must then get a rearrangement of the remaining double bond to lớn the 2 position. But that would produce a primary carbocation, which is surprising given that it will be less stable than the senangngucnoisoi.vnndary one.So I guess I must be missing something
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It's just nangngucnoisoi.vnmpetition between the two isomers, the 1,2-addition product will khung faster since it has the more stable senangngucnoisoi.vnndary carbocation but with enough energy the 1,4-addition sản phẩm will dominate since the internal double bond is more thermodynamically stable.edit: sorry, this is more of an undergraduate explanation


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I think you mean buta-1,3-dieneIt doesn't matter which double bond opens first (as they are indistguishable). A Br will bond khổng lồ the kết thúc carbon và you will size the senangngucnoisoi.vnndary carbocation.So far so good.I would then expect the other bromine lớn go to the 2 position, leaving the other double bond where it is and forming 1,2-dibromobut-3-ene.If it doesn't, you must then get a rearrangement of the remaining double bond to the 2 position. But that would produce a primary carbocation, which is surprising given that it will be less stable than the senangngucnoisoi.vnndary one.So I guess I must be missing something
It's just nangngucnoisoi.vnmpetition between the two isomers, the 1,2-addition hàng hóa will khung faster since it has the more stable senangngucnoisoi.vnndary carbocation but with enough energy the 1,4-addition hàng hóa will dominate since the internal double bond is more thermodynamically stable.edit: sorry, this is more of an undergraduate explanation

It's just nangngucnoisoi.vnmpetition between the two isomers, the 1,2-addition product will khung faster since it has the more stable senangngucnoisoi.vnndary carbocation but with enough energy the 1,4-addition hàng hóa will dominate since the internal double bond is more thermodynamically stable.edit: sorry, this is more of an undergraduate explanation


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Aha! I am just so kinetic. Can't help it, I guess
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