Questions related to the chemical and physical influences that influence the rate and probability of chemical reactions.

learn more… | top users | synonyms

1
vote
0answers
25 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 ...
0
votes
1answer
48 views

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 ...
4
votes
0answers
35 views

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 ...
2
votes
2answers
96 views

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 ...
0
votes
0answers
50 views

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 ...
9
votes
1answer
143 views

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 ...
3
votes
0answers
40 views

Neighbouring group participation in Sn1/Sn2 reaction

It is known that chlromethoxyethane forms stable carbonium ions based on Nobel prize Chemist George Olah research Olah's method. This would indicate that chloromethoxyethane reacts through Sn1 ...
12
votes
2answers
280 views

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 ...
3
votes
1answer
76 views

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 ...
0
votes
0answers
16 views

Voltage initiated solid removal reaction?

I have a problem I need to solve and I am at a loss for a chemical reaction or process to begin. I have a voltage from a battery operated system and I need to dissolve or remove a structural solid. ...
10
votes
2answers
267 views

Reason behind Le Chatelier's principle

I understood Le Chatelier's principle perfectly but my question is why? Why should a system try to reverse any change that has been done to it? I understand equilibrium constant, mole concept and ...
3
votes
0answers
21 views

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 ...
3
votes
0answers
151 views

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 ...
1
vote
1answer
85 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 ...
1
vote
0answers
19 views

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 ...
0
votes
1answer
29 views

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 ...
6
votes
1answer
84 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 ...
3
votes
0answers
49 views

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 ...
1
vote
1answer
52 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 ...
3
votes
1answer
84 views

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.
0
votes
1answer
42 views

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 ...
0
votes
0answers
34 views

Calculation of concentration of component at catalyst surface

I am struggling a bit with an external diffusion problem. I am trying to calculate the concentration at the surface (as well as surface reaction rate) and would like some help or guidance. Here is ...
3
votes
0answers
185 views

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^+ + ...
3
votes
2answers
120 views

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 ...
2
votes
0answers
37 views

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?
6
votes
0answers
142 views

By how many pKa units will the pKa value of a ketone be minimized by addition of a lewis acid?

I want to enolize a ketone, let's take for instance acetone with a pKa value of about 20 (in $\ce{H_2O}$). Now I'd like to know if there exist rule of thumb (I don't think so), by how many pKa units ...
4
votes
0answers
209 views

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 ...
5
votes
2answers
21k views

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 ...
3
votes
2answers
211 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 ...
6
votes
1answer
67 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 ...
0
votes
1answer
133 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 ...
2
votes
1answer
547 views

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 ...
1
vote
1answer
71 views

The reaction of Nitrogen trichloride explosion is 2NCl₃(l) -> N₂(g) +3Cl₂(g); which of the graphs represents this reaction? [closed]

This is a homework question and I'm finding it hard to understand, so an explanation why will be great. Image of graphs a, b, c, d Thanks!
1
vote
1answer
364 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 ...
2
votes
0answers
39 views

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 ...
10
votes
1answer
10k views

Furan and maleic anhydride: Why is the major product exo?

For most Diels-Alder reactions, the product is endo because there are favorable interactions between the newly forming pi-bond and the electron withdrawing groups of the dienophile. Why is the ...
2
votes
1answer
92 views

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 ...
1
vote
2answers
666 views

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 ...
1
vote
1answer
181 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 ...
-1
votes
1answer
244 views

Which of the following will react? [closed]

Which of the following elements will react with HCl to produce Hydrogen gas: Al Ag Zn Mg Cu Au
16
votes
2answers
3k views

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 ...