Questions tagged [reaction-coordinate]
Questions related to abstract one-dimensional coordinates which represent progress along a reaction pathway.
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How change in potential energy corresponds to change in enthalpy?
So while reading about activation energy , I came across this graph :
Here, change in potential energy of reactant and product is depicted as ${ΔH}$, but at constant pressure and temperature , ...
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2answers
51 views
Organic-catalysis microwaves [closed]
When we perform a organic reaction without any addtional catalyst except that the reaction is carried out under microwave condition we can accelerate this reaction in comparison with one under heating ...
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1answer
657 views
How to draw a reaction coordinate diagram for SN1 mechanism?
How would you draw a reaction coordinate diagram for an SN1 mechanism with the following conditions?
each step in the mechanism (there are 2 steps) is favorable
the second step of the mechanism is ...
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0answers
94 views
Potential energy surface in transition state theory
I would like to study the typical reaction from the transition state theory:
$$\ce{AB + C <=> ABC^‡ -> A + BC}$$
Assuming $\ce{ABC^‡}$ is a colinear molecule, the potential energy surface of ...
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0answers
185 views
Why is the top SN2 reaction faster? (Molecular Orbital Theory)
I'm having trouble understanding why the top SN2 reaction proceeds faster. I know that benzylic and allylic halides react faster in SN2 reactions than non-conjugated halides. I think it's because the ...
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1answer
78 views
Endothermic or Exothermic [closed]
Is an endothermic reaction always endothermic at all conditions of pressure, temperature etc.? Similarly for exothermic... I mean is sign of ∆H always the same as sign of ∆H°?
This might seem to be a ...
4
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1answer
379 views
Hessian Matrix and Physical directions: Potential Energy Surface
How do the eigenvectors of the Hessian Matrix for potential energy surface correspond directly to the physical directions of translation, rotation and vibration?
I see that they might correspond to ...
3
votes
1answer
321 views
Relationship between Gibbs free energy and potential energy (related to reaction coordinate diagrams)
For a rate law, the rate constant $k$ is given by the equation
$$\ln k = \ln A - \frac{E_\mathrm{a}}{RT}\tag{1}$$
If $k_\mathrm{fwd}$ is the forward rate constant and $k_\mathrm{rev}$ is the reverse ...
4
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2answers
701 views
Y-axis of the reaction co-ordinate graph
In the graph of the reaction co-ordinate, is the $y$-axis that is used $∆H,$ $∆U$ or $∆G$?
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AP Chem Question about Reaction Rate - Confused?
I found this question in the AP Chem book, and I understand why B is the answer (as the answer key says). However, I don't understand why D is not also correct.
The question is:
A multistep reaction ...
0
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1answer
526 views
Probability of the single molecule reaction to happen
I am trying to simulate the single particle second order reactions with known rate constants $k_1$ and $k_{-1}$ in Python. The point of this simulation is to fit the real experimental data to the ...
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1answer
52 views
Is it possible to define the coordinates of an atom using other coordinates while optimizing in gaussian 16?
I know it is possible to fix the value of composite expressions using generalized internal coordinates (gic) in gaussian 16. But is it possible to assign that value to the coordinate of another atom.
...
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1answer
54 views
Finding direction of the reaction using Affinity of the reaction
I encountered following reaction:
$$\ce{CO + 1/2 O2 -> CO2}$$
I am provided with the composition of the various gases at $\pu{1000K}$ and am asked the direction of the reaction by finding the ...
3
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1answer
918 views
Auto-catalysis Mechanism
I just read about the theory of auto-catalysis, and here's one thing which is sort of unclear to me:
In this type of catalysis, one of the reaction product catalyses the reaction. For example, in ...
8
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1answer
334 views
Is there any empirical upper limit for order of reaction?
I learned from one of my teachers that empirically reaction with order greater that 3 are never found. But, I am suspicious of the truth value of his claim.
To add to my suspicion there is this paper ...
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2answers
3k views
Why is law of mass action only applicable for elementary reaction?
Why can't we apply law of mass action for non-elementary reaction? Why does is vary with the rate law in case of non-elementary reactions?
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2answers
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Law of Mass action VS Rate law [duplicate]
The Law of mass action has 2 parts - the equilibrium rate part & the reaction rate part.
The "reaction rate part" states that rate of a reaction is directly proportional to the product of active ...
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0answers
58 views
How to determine which normal mode leads to the transition state (numerically)? [closed]
I would like to get the normal mode of vibration which leads to the transition state. Do you know any software for this problem? If no, could you offer an algorithm to generate it? By the way, is ...
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1answer
72 views
Find reaction heat of a reaction [closed]
1) A(s)+O2(g) →Ao2; ΔH^0=-394kj/mol
2)AO(g)+ $\frac{1}{2}$O2(g) →AO2; ΔH^0=-283kj/mol
3)A(s)+ $\frac{1}{2}$O2(g) →AO(g); ΔH^0=-Xkj/mol
Find the value of X? I want to know How to find this value.
2
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0answers
93 views
rate constant via flux-flux correlation function for linear potential energy surface
How does one calculate fully quantum mechanical rate ($\kappa$) in the golden-rule approximation for two linear potential energy surfaces?
Attempt:
Miller (83) proposes $\kappa=\int{Tr[\exp{(-\beta\...
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1answer
71 views
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0answers
357 views
How to sketch reaction coordinate plot from mechanisms?
I am interested in learning about strategies for drawing reaction coordinate plots from the reaction mechanism. The sketches I am after don't need to be highly accurate or precise, but should reflect ...
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1answer
465 views
Intrinsic Reaction Coordinate - Converting To Reaction Coordinate with Units of Distance
I've located a transition state and ran two IRC calculations (one to get to the product and one to get to the reactant). Is there some type of way of approximating the IRC to something that has units ...
2
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1answer
98 views
How to select a schematic of the coordinate vs energy representing a rearrangement reaction?
Here's the question
For a reaction to take place the net energy should go down, and thus option (d) can be discarded.
We are now left with options (a), (b), and (c).
A $3^{\circ}$ carbocation is more ...
8
votes
1answer
150 views
Ballistic behavior of molecules on potential energy surfaces
I came across the following sentence in a publication$^1$: "At this point we have to remember that the computed MEP path [sic] represents the reaction in the absence of any kinetic energy, while in ...
5
votes
3answers
628 views
Intrinsic Reaction Coordinate calculation-- both sides of TS lead to same minimum
I am currently trying to find an addition transition state and verify it using an IRC calculation. I have found a good candidate, but the IRC calculation gives the same minimum on each side of the ...
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1answer
256 views
Regarding the free energy requirements for reacting gases
Continued from my previous question here.
With regards to the Boltzmann factor, I am confused on what type of terms we can substitute for E. I know kinetic energy is one, free energy as well, but ...
3
votes
0answers
988 views
Are multiple transition states possible? Criteria to choose the correct one?
I am studying a reaction using electronic structure methods using various software packages (ORCA,GAMESS, G09) and have found two possible transition structures between product and reactant. Both have ...
9
votes
2answers
2k views
Reaction Pathways: What to do when IRC geometries are relaxed (optimized) and the energy changes significantly
The Story:
Reaction pathways can be difficult things to deal with using electronic structure methods. Intrinsic reaction coordinates (IRCs) can be determined a number of ways (a discussion of these ...
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1answer
100 views
How to trace an energy versus time diagram?
I'm looking for data to create a simple graph of an exothermic or endothermic reaction but can't find any.
Could someone help me with some enough data to create a simple graph displaying energy as ...
8
votes
1answer
830 views
Intrinsic Reaction Coordinate - What does 'Connectivity' really mean?
I am currently in the process of connecting transition state (TS) structures to other minima in order to determine a reaction pathway. Now I understand the basic concepts of this method. You start ...
4
votes
2answers
189 views
What is the energy package released to the outside world?
Consider a chemical reaction where two different particles form another one
$$\ce{O + O_2 -> O_3}$$
I find it confusing how this can be an exothermic process. How to picture the release of $+\...
25
votes
1answer
8k views
What does "reaction coordinate" mean? What does it mean when a reaction has TWO reaction coordinates?
I'm familiar with the concept of a reaction coordinate from high school chemistry as some generic conformational parameter that all of the intermediate states of a chemical reaction lie upon. Recently,...
