AAMC 8 BS question

[natusss]

Could someone explain 153 and 154 to me? I dont think I even understand what they are asking.
Thanks

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[Creightonite]

wow, i am not alone on those two questions!

 

[Mah]

153- basically asking why "kinetically-favored" products are favored?
That's because they have a lower activation energy as compared to other products and are also formed quickly

154- asking why "thermodynamically-favored" products are favored?
Because they are more stable at equilibrium.

An example could be bromination and chlorination. Chlorination is kinetically favored, hence it is produced much more quickly, usually happens at terminal carbons and produce mixture of compounds. On the other hand, bromination is thermodynamically favored, thus it usually happens at the tertiary carbon, after the formation of tertiary carbocation, which is the most stable.

I hope some of this makes sense. Correct me if im wrong though.

 

[kaybam20]

153- basically asking why "kinetically-favored" products are favored?
That's because they have a lower activation energy as compared to other products and are also formed quickly

154- asking why "thermodynamically-favored" products are favored?
Because they are more stable at equilibrium.

An example could be bromination and chlorination. Chlorination is kinetically favored, hence it is produced much more quickly, usually happens at terminal carbons and produce mixture of compounds. On the other hand, bromination is thermodynamically favored, thus it usually happens at the tertiary carbon, after the formation of tertiary carbocation, which is the most stable.

I hope some of this makes sense. Correct me if im wrong though.

Also,kinetically favored prodeucts are firmed because they have a low activation enegy giving them the opportunity to from early at low temperatue. However at higher temperatures and under equilibrium condition, product formation always favor the stable product. Hence underr equilibrium some Kineticaly favored product are eventually transformed in to the more stable product.

 

[natusss]

So...
the kinetically favored product has lower activaton energy and is therefore able to go faster.
the thermodynamically favored product is more stable, so if you increase the temperature and/or allow the reaction to reach eq you will see more of the thermo product?

Thanks for helping! The answer key did not make any sense!

 

[Creightonite]

I got confused on this question because i thought kinetics and thermodynamics are different things. So I ended up throwing out the answers that were brining them together.