Talk:MRD:ar3015
Great work! Your wiki is concise and to the point. Your reasoning is sound throughout! Here are a couple of pointers to further improve:
- Expression: I sometimes find it difficult to follow your writing. Especially your use of relative pronouns and relative clauses is confusing. Consider the "Determining the activation energies" section for example. Most of your sentence start with "this". While I understand what you are saying, it does require effort to read. I also think that you're using a number of superfluous words (unfortunately this happens often in scientific literature, so I don't blame you for it). Take the sentence "Due to the conservation of energy, as the kinetic energy has increased this means the potential energy must've decreased which is demonstrated in the potential energy graph." for instance. You've used four linking or relative words in one sentence. I would rewrite this as "Due to the conservation of energy, any increase in kinetic energy is balanced by a decrease in potential energy. This is demonstrated in the potential energy graph.". Lastly, a word about the use of "if" (this is nit-picking already). "If we invoke Hammond's postulate, the early transition state indicates an exothermic reaction." An early transition state always indicates an exothermic reaction, whether or not you invoke Hammond's postulate. A neater way of expressing your sentence is: "Within Hammond's postulate, an early transition state indicates an exothermic reaction." Now it is clear that you are talking about something enclosed in the framework of a specific theory.
- Answers to questions:
- Transition State properties: First, remember that we are dealing with a 2D problem. It is true that both derivatives are 0 at minima, maxima and saddle points. Furthermore you're right in saying that the second derivatives allows you to distinguish between the different types of extrema. However, since this is a 2D problem there are three types of second derivatives (, & ). Considering that a saddle point is a maximum in one direction and a minimum in the other, can you come up with a criterion for the second derivatives to determine whether a point is a saddle point?
- TS theory: I'm in two minds about this answer. You've done well in identifying a conflict of your own data with the theory, but your invocation of quantum mechanics is out of place. The simulation you ran does not contain QM, so QM can't be responsible for any deviations from the theory you see in your experiments.
- Determining the activation energies: Do you think the geometries you obtained for reactants and products are indeed their final geometries? What would happen if you increased the time frame of your simulations? Your activation energies are slightly too low; can you figure out why?
- Polyani's Rules: Your reasoning is sound based on the evidence you presented. However, basing a judgement on one experiment for each setting is dangerous. I would like you to investigated the four cases (early TS, high vib; early TS, low vib; etc.) more thoroughly so you gain a statistic understanding of how often the theory works and how often it doesn't.