Questions tagged [reaction-coordinate]

Questions related to abstract one-dimensional coordinates which represent progress along a reaction pathway.

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Impact of temperature on an Energy profile diagram

What happens to the energy profile diagram if you increase the temperature of the system? From my understanding, I think the whole diagram would shift upwards, as the reactants and products will both ...
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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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2 answers
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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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1 vote
1 answer
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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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2 votes
0 answers
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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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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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1 vote
1 answer
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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 ...
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4 votes
1 answer
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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 ...
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3 votes
1 answer
406 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 ...
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4 votes
2 answers
790 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 ...
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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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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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2 votes
1 answer
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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 ...
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3 votes
1 answer
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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 ...
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9 votes
1 answer
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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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2 votes
2 answers
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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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6 votes
2 answers
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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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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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1 answer
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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.
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2 votes
0 answers
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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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1 answer
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Exothermic reaction [closed]

Please someone explain me the solution of this question.
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1 vote
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360 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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1 vote
1 answer
479 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 ...
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2 votes
1 answer
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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 ...
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8 votes
1 answer
153 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 ...
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5 votes
3 answers
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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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1 vote
1 answer
263 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 ...
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3 votes
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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 ...
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9 votes
2 answers
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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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1 vote
1 answer
103 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 ...
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8 votes
1 answer
834 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 ...
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3 votes
2 answers
192 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 $+\...
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25 votes
1 answer
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,...
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