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A bit more detail about how catalysts speed up chemical reactions - to get from products to reactants you need to climb an energy barrier to get to something ca

A bit more detail about how catalysts speed up chemical reactions - to get from products to reactants you need to climb an energy barrier to get to something called the "rate-determining transition state". What catalysts do is stabilize or reduce the amount of energy (called activation energy) required to reach this transition state, and by doing so, the reaction goes faster. The stability is achieved through interactions between the rate determining transition state and the catalyst. Sometimes the catalyst causes a change in the reaction mechanism leading to a different rate-determining transition state as well. EDIT: pretty sure this was Ben List's first paper on this idea: https://pubs.acs.org/doi/10.1021/ja994280y https://pubs.acs.org/doi/10.1021/ja994280y David MacMillan's first paper on this idea: https://pubs.acs.org/doi/abs/10.1021/ja000092s https://pubs.acs.org/doi/abs/10.1021/ja000092s

hi41 5y ago
Layperson here. It’s my understanding that energy can neither created not destroyed. So if a reaction needs more energy otherwise, then how do catalysts provide that extra energy needed for the reaction yet not fail energy conservancy law?
- ace2358 5y ago
  I don’t think they provide the energy, they change the required energy for a reaction to occur. My understanding is that is can happen due to the physical structure of the catalyst changing the electronic configuration of the molecules being reacted. I think often instead of the two molecules coming into contact and reacting, the two molecules and the catalyst come into contact. It’s a whole different reaction, but the catalyst molecule doesn’t change its composition and is left unchanged after the reaction. I guess maybe a terrible analogy would be you’re trying to cross a flat field but there is a large group of animals, say, cows in the way. You’d never be able to get through the crowd of cows without exerting a lot of energy. Then suddenly a dog, catalyst, come over and starts shooing off the cows. Now the cows have moved out of the way and the flat field is clear. You can now make the journey while expending less energy. Hmm maybe someone else can explain it better!
- infogulch 5y ago
  You can think of the energy of the reactants and products as valleys separated by a mountain. The "normal" reaction requires the reactants in their base energy state (the bottom of the valley) to climb up the whole mountain, thus it will be very slow. The "just add enough heat" method is like flooding the whole mountain range up to the peak -- it technically works but causes other issues. Adding a catalyst is like digging a tunnel through the mountain.

hi41 5y ago

Layperson here. It’s my understanding that energy can neither created not destroyed. So if a reaction needs more energy otherwise, then how do catalysts provide that extra energy needed for the reaction yet not fail energy conservancy law?

ace2358 5y ago
I don’t think they provide the energy, they change the required energy for a reaction to occur. My understanding is that is can happen due to the physical structure of the catalyst changing the electronic configuration of the molecules being reacted. I think often instead of the two molecules coming into contact and reacting, the two molecules and the catalyst come into contact. It’s a whole different reaction, but the catalyst molecule doesn’t change its composition and is left unchanged after the reaction. I guess maybe a terrible analogy would be you’re trying to cross a flat field but there is a large group of animals, say, cows in the way. You’d never be able to get through the crowd of cows without exerting a lot of energy. Then suddenly a dog, catalyst, come over and starts shooing off the cows. Now the cows have moved out of the way and the flat field is clear. You can now make the journey while expending less energy. Hmm maybe someone else can explain it better!
infogulch 5y ago
You can think of the energy of the reactants and products as valleys separated by a mountain. The "normal" reaction requires the reactants in their base energy state (the bottom of the valley) to climb up the whole mountain, thus it will be very slow. The "just add enough heat" method is like flooding the whole mountain range up to the peak -- it technically works but causes other issues. Adding a catalyst is like digging a tunnel through the mountain.