why are eliminations favored over substitution under high temp.??

[tRNA]

---

Members don't see this ad.

hi All,
I am struggling with this concept, I have the question and the answer but I just don't understant the concept, here is the question:

Increasing the temperature favors elimination reactions over substitutions. what reason can you give to account for this?

answer: Eliminations are favored at higher tempratures because eliminations have higher free energies of activation than substitution. the reasoning behind this is due to the fact that eliminations have a greater change in bonding ( more bonds are broken and formed). By giving more molecules enough energy to sumount energy barriers, increasing the temperature increase the rates of both substitutions and eliminations, however, because the energy barrier for eliminations are higher, the proportion of molecules able to cross them is significantly higher.
I specifically don't understand why is the activation energy higher for eliminations reactions....is it because more bonds are broken in eliminations rxns than in substitution rxns?? and secondly I don't understand the part I highlighted in green, this is how I understood this part: is it saying that at higher temp. more molecules can cross a higher activation barrier than a low activation barrier?? I just don't get it 🙁

 

[Richnator]

Whenever you break bonds, it requires a certain amount of activation energy. Therefore, since elimination requires more bonds to be broken than substitution, it will take a higher energy input to surpass this requirement, the activation energy. Hence, elimination is favored in higher temperatures. Since, elimination will never get the energy to surpass this activation energy in lower temperatues, subsitution is more probable during low temperatures. I don't know if I can word it more simply than that.

Hope this helps,
Rich

 

[joonkimdds]

Whenever you break bonds, it requires a certain amount of activation energy. Therefore, since elimination requires more bonds to be broken than substitution, it will take a higher energy input to surpass this requirement, the activation energy. Hence, elimination is favored in higher temperatures. Since, elimination will never get the energy to surpass this activation energy in lower temperatues, subsitution is more probable during low temperatures. I don't know if I can word it more simply than that.

Hope this helps,
Rich

is this chemisty question?

 

[Richnator]

organic chemistry.

 

[tRNA]

Thanks Rich