Questions tagged [reaction-control]

Questions related to the chemical and physical influences that influence the rate and probability of chemical reactions. Not to be confused with [catalysis] or [reaction-mechanism].

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Chemical equilibrium and Le Chatelier Braun for ammonia production

In the book of Chemical, biochemical and engineering thermodynamics 4th edition from Stanley I. Sandler (Wiley, 2006), there is a problem about the ammonia producing reaction at page 770. 13.17 The ...
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Rate determining step

The formation of the cation is the rate-determining step. we can look at this in two ways. Either that a cation is an unstable species and so it will be formed slowly from a stable neutral organic ...
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Is there wavefunction interference between alternate reaction pathways?

I'll give a specific example to clarify my question. If we look at the approach of chloromethylenecarbene's electron pair to cis-2-butene in the reaction of creating 1-chloro-2,3-dimethylcyclopropane, ...
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863 views

Calculating time taken for a set percentage of a reaction to occur based on half-life

The half-life of a first order homogenous gaseous reaction: $\ce{SO2Cl2 -> SO2 + Cl2}$ is 8.0 minutes. How long will it take for the concentration of $\ce{SO2Cl2}$ to be reduced to 1% of the ...
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Reactivity towards SN1 reaction

In the following compounds , we have to find order of compounds of their reactivity towards SN1 reaction. According to me , we should compare carbo cation stability which is formed as an ...
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Increasing C-alkoxycarbonylation of enolates

I am working with N-tosyl-2-piperidone and attempts to use the lithium enolate of this compound to perform an nucleophilic acyl substitution reaction on an several chloroformate esters in THF has lead ...
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Limit the production of hydrogen in a small container

I have to produce hydrogen at a near-constant pressure inside of a really small container without using an automatic pressure release value. I would like the pressure to be relatively high, but the ...
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10k views

Relationship between Gibbs free energy, enthalpy, entropy and rate of reactions

I'm having a little trouble constructing the bigger picture of chemical reactions. From the collision theory we know that molecules react if: 1) they collide 2) they collide bearing a sufficient ...
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Does changing the volume of a reactant affect the rate of reaction? Does changing the volume of HCl affect the rate of a Mg & HCl reaction?

I'm doing a experiment in which I'm testing the affect of the concentration of a reactant on the rate of reaction. The reaction is between Magnesium and Hydrochloric Acid and so I'm changing the ...
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Is there a way to force C-protonation of an enolate?

In another question, I mentioned that O-protonation of an enolate followed by tautomerization may lead to increased amounts of the thermodynamic product over the kinetic product (when those are ...
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Thermodynamic versus kinetic reactions

In a lecture, teacher said "Nucleophilicity is about 'kinetic', and basicity is about 'thermodynamic'" but I saw the picture below from another source. Here, both pathways start with an acid/base ...
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Chlorination of propene at 773 K

The first step of preparation of glycerol with propene involves the chlorination of of propene at 773 K. It results to form allyl chloride. However the halogenation of alkenes generally give vicinal ...
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Why is −78 °C a magic temperature for organic reactions?

In many organic reactions that I have seen, running the reaction at $\mathrm{-78\ ^\circ C}$ seems to be quite a popular choice, but I've never seen any explanation for this. What makes this ...
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Does (chloromethoxy)ethane react in a bimolecular or monomolecular mechanism?

It is known that (chloromethoxy)ethane forms stable carbonium ions based on Nobel prize Chemist George Olah research Olah's method. This would indicate that (chloromethoxy)ethane reacts through $\...
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Thermodynamic and kinetic products - carbocation stability

The professor wants to know which is the thermodynamic product and which is the kinetic product. He says there are only two products - the two on the right that result from the resonance-stabilized ...
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SN1 vs SN2 in low concentration of nucleophile

Why is SN1 mechanism favoured by low concentration of nucleophilic reagent? It is a first order reaction so shouldn't the reagent be in excess? Also higher the concentration of reagent faster the ...
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How do I find the rate constant in this situation?

Say I have two kinds of molecules $A$ and $B$. The molecules of type $B$ are small and bind onto molecules of type $A$. (Any number of them may do so, but in practice this number is $\leq 8$.) We ...
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How does pH affect the degradation of ascorbic acid (vitamin C)?

I know that vitamin C degrades over time (as I understand through oxidation). However, I am having trouble understanding how changing the pH of the solution in which the vitamin C is affects the rate ...
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531 views

What's the difference between "conversion" in condensation polymerization and in radical polymerization?

The conversion in condensation polymerization is defined as the fraction of functional groups reacted, $$p=\frac{[M]_0-M}{[M]_0}$$ while in radical polymerization it's defined as the fraction of ...
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Can there be gaps in autoignition temperatures?

I recently saw a request for solids that auto-ignite between 80C and 160C. I can't find any, and none have yet been suggested. Which leads me to the theoretical question: Is it possible for there to ...
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Controlling the reaction of alcohols with acid to either ether synthesis or elimination

Let’s say you take ethanol: $\ce{CH3-CH2-OH}$ and you add an acid and heat. You can get water, the acid, and $\ce{CH2=CH2}$ (a dehydration reaction). However, you can also get $\ce{CH3-CH2-O-CH2-CH3}$,...
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807 views

Why does sulfonation of alcohols even work?

I am now near the end of organic chemistry 2, and I'm trying to understand the patterns of reactions so that I can predict them rather than brute force memorizing all of them. Looking at the ...
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Clash between thermodynamic and kinetic processes

I have often come across reactions where kinetic and thermodynamic processes give completely different outputs. I was told that in such cases check temperature, if temperature controlled, then take ...
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328 views

Strip away a small amount of aluminium with household chemicals

I'm trying to turn a 6″ diameter mirror (I have spares) into a two-way mirror. It shouldn't be too hard to remove the backing, but then I need to remove most, but not all of the Aluminium plating. My ...
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How does the solvent determine whether mono- or tribromination of phenol occurs?

In phenol, the $-\ce{OH}$ group activates the benzene ring towards electrophilic substitution. But why is it that the electrophilic bromination of phenol gives trisubstitution (forming 2,4,6-...
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Relationship between Productivity and Yield

I am trying to formulate an optimization problem. Can you help me understand the definition of productivity and yield? Why is there a trade-off between them during the reaction? Thanks in advance.
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Why is the sneaky method of smothering a grease fire more effective?

In this demonstration, a grease fire is temporarily extinguished if you put the cover on the pan, but reignites as soon as you take the cover off. However, if you slowly slide the cover across the ...
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How to inhibit Mn2+ autocatalysis in the oxalate-permanganate reaction?

It is well known that permanganate in acidic solution can oxidize oxalate ions (or oxalic acid). The reaction produces $\ce{Mn^2+}$, which catalyzes this very reaction. $$\ce{2MnO4^- + 16H^+ + 5C2O4^...
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Why does the Birch reaction not yield fully saturated products?

Why isn't benzene reduced all the way down to cyclohexane when performing a Birch reaction? (Why is it not reduced further?) Similarly for the reaction with sodium dissolved in liquid ammonia, why ...
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Grignard reaction - exchange of groups

Why is this reaction successful: Why doesn't metal-halide exchange occur easily to get Ar-MgCl and R-Br?
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What makes a compound a dehydrating agent?

When a carboxylic acid with low molecular weight is heated with $\ce{P2O5}$ we get the corresponding anhydride. My book says that this reaction happens with dehydrating agents such as $\ce{P2O5}$. I ...
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What are the differences between diesel and unleaded gasoline?

I am curious about the flammability of diesel fuel and its properties, as I don't deal with it on a regular basis (at all). In particular, I want to know how the fuel works when powering a diesel ...
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1k views

Does pressure affect non-gaseous reactions?

Pressure holds a great significance when it comes to reactions involving gaseous species. Changing pressure can affect the kinetics and even mechanisms of such reactions. However, does pressure hold ...
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858 views

Why does addition polymerisation of high density poly(ethene) use low temperature and pressure?

Logically thinking, I thought that it would be high pressure and high temperature that would create high density poly(ethene)... However, that's not the case. Is it because of the catalyst? Why is the ...
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684 views

Does a change in partial pressure for a gas-solid reaction, changes the equilibrium?

This is my reaction, $$\ce{Cd (g) + 1/2 Te2 (g) -> CdTe (s)}.$$ Considering the solid CdTe, $$K = P_{\ce{Cd}}^\mathrm{Eq}\cdot \left(P_{\ce{Te}}^\mathrm{Eq}\right)^{\frac{1}{2}}$$ I only have ...
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Can we do combustion caused by limited supply of air in a lab? How?

For example Ethyne in combustion by limited supply of air $$ \ce{ 2C2H2 + 3O2 ->[\Delta] 2CO2 + 2H2O + 2C } $$ vs. $$ \ce{ 2C2H2 + 5O2 -> 4CO2 + 2H2O + Energy } $$ What are the limits ...
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Relationship between surface area of electrode and reaction rate of hydrogen in fuel cells

I am looking at the effects of increasing the surface area of which the flowing hydrogen fuel is in contact with the anode in a fuel cell. At the anode the hydrogen is catalytically split into ...
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908 views

Free rotation of sigma bonds; diastereomer formation; thermodynamic and kinetic products

For the reaction of 1,3-butadiene with DBr (D = heavy hydrogen), I found that several possible products could be formed. Kinetic products A pair of enantiomers is formed. One of the pi bonds ...
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Other than heating, is there any evidence that normal RF radiation (say, microwave range) can affect chemical reactions?

There's been a lot written (and debunked) about alleged biological effects from RF radiation, even when it's too low powered to cause heating effects or ionization. Is there any chemical reason to ...
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Does anyone know where I can find the reaction rate coefficient and design equation for the electrolysis of brine and sodium hydroxide solution?

equation 1) $\ce{2 Cl^{–} -> Cl_2 + 2e^{-}}$ equation 2) $\ce{2 H2O + 2 e^{–} -> H2 + 2OH^{–}}$ These equations are the key reactions in the chlor-alkali process. I want to model a reactor ...
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Equilibrium rate constants forward and backwards

Correct me If I am wrong, given a reaction at equilibrium, if we say add more concentration of products to the reaction, the rate going backwards would increase to try to get back to equilibrium. I ...
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935 views

Unfavorable reactions

How can you make an unfavorable reaction go backwards? From my understanding if we wanted a reaction at equilibrium to go backwards (i.e. form reactants from products), we would add more product into ...
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Why does water favour nucleophilic substitution over elimination?

The two broad ways a halogen can leave a haloalkane are nucleophilic substitution and elimination reactions. I was told that elimination reactions (that form a double bond as a $H^+$ is also removed) ...
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Michael reaction or nucleophilic attack at the alpha carbon of an alpha-beta-unsaturated ketone?

What conditions promote a nucleophile to undergo the Michael reaction over the nucleophilic attack at the alpha carbon of the carbonyl group in an alpha-beta-unsaturated ketone? I'm looking for an ...

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