Questions tagged [catalysis]

This tag is appropriate for reactions, their mechanisms, their kinetics, when catalysts of any kind are involved.

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How does Palladium dissociate H₂ so easily?

If I understand correctly, $\ce{H2}$ in the presence of $\ce{Pd}$ readily dissociates as it dissolves into the metal. With the dissociation energy for the $\ce{H—H}$ bond being so large, how is this ...
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Platinum group metals: Why are platinum and palladium great catalysts and not the others?

Platinum and palladium are great catalysts. At the same time, other metals of the so-called platinum group metals are not. What are the atomic level reasons for this?
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Energy-efficiency aside, what are the chemical constraints on CO₂ capture and methanation?

Synthesising $\ce {CH4}$ from air and water (in a non-biological process) has been proposed as one form of energy storage. What are the chemical constraints at play here? That is to say, what sort of ...
410 gone's user avatar
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Won't the net effect of a catalyst be zero if it creates a new path with lower activation energy?

A catalyst will provide a new path with a lower activation energy (Figure 1). Won't this mean the forward and backward reactions will both speed up (as they both have a lower activation energy path to ...
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Why is pyridine used when making tosyl esters from alcohols?

Tosyl chloride is used to make a hydroxyl group into a better leaving group. However, when the reaction of tosyl chloride and an alcohol occurs, a weak base such as pyridine should be used. Why?
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Difference between Lindlar and Rosenmund catalysts

Is there any difference between the Lindlar and Rosenmund catalysts? I've checked around, and it seems the same compounds are used to make both. Is there a difference in their reactivities or are they ...
Black Jack 21's user avatar
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What is the chemistry behind this "petrol from air" technology?

A recent news report in the UK claimed a breakthrough in making a petrol equivalent from carbon dioxide and water: A small British company has produced the first "petrol from air" using a ...
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How does the choice of metal (oxide) catalyst affect the range of unsaturated compounds that can be hydrogenated?

In the hydrogenation of unsaturated compounds with hydrogen gas and a catalyst, the choice of palladium on carbon is able to hydrogenate alkenes and alkynes, but is unable to hydrogenate aromatic ...
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13 votes
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Is it possible to make an anticatalyst?

I'm wondering if it is possible, theoretically, to create compounds which perform the opposite function of a catalyst (thus an anticatalyst). That is to say, could a compound be made which raises the ...
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A misunderstanding about the energy profile of reactions with a catalyst involved

All of us are aware of the importance of the catalysts in bio-chemistry. For a high school learner like me, catalysts ,and therefore, enzymes play a bridge-like role that connect high school bio to ...
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What might serve as an initial starting photocatalyst for this large water-splitting solar simulator?

Question: What might serve as an initial starting photocatalyst for this large water-splitting solar simulator? Surely there must have been some planned experiments! The Gizmodo article Insane Light ...
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What is the meaning of writing a catalyst name with two compounds split by a hyphen?

In literature, sometimes I see catalysts written with "-" between elements/compounds. Does this mean the first element/compound is supported on the second, or is the second a promoter? (e.g. $\ce{Fe}$-...
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Is there a catalyst that will reduce an alcohol to an alkane?

There are many reduction methods of going from an alcohol to an alkane: http://www.transtutors.com/chemistry-homework-help/hydrocarbons/reduction-of-alcohols.aspx And there are catalytic methods of ...
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What is the chemical formula of KIT-6?

I have seen KIT-6 used in literature as a catalyst support, but cannot find the chemical formula for it.
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Difference between nickel catalyst and Raney nickel catalyst

Many times I have seen the catalyst as Raney nickel instead of nickel catalyst. Raney nickel catalyst is developed by Murray Raney, and I think Raney nickel catalyst and nickel catalyst are two ...
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Isomerisation of alkanes under Lewis acidic conditions

My textbook says: n-Alkanes on heating in the presence of anhydrous aluminium chloride and hydrogen chloride gas isomerise to branched chain alkanes. But no mechanism is given. After a little ...
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What is an example of chemical reaction that can be assisted by both an inorganic catalyst and an enzyme?

I have been researching chemical reactions of inorganic catalysts and enzymes and cannot find a chemical process where an inorganic compound can be replaced by an enzyme (or vice versa) and have the ...
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Reaction intermediates of MnO2 catalyzed H2O2 decomposition reaction

Manganese dioxide catalyzes the decomposition of hydrogen peroxide to water and oxygen gas. But what are the intermediates in this catalyzed reaction?
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11 votes
1 answer
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Stability of transition and post-transition metal alkoxides

Many transition metal alkoxides are seen in chemistry, for instance those of $\ce{Ti, Sn}$ and $\ce{Al}$, and in particular one of those of aluminium has its own role in the MPV reduction reaction. I ...
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11 votes
1 answer
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Terminal Alkyne in Suzuki Coupling

I've done a very similar reaction to the one below but by TLC I observe only starting materials. It's super clear that nothing else is going on. Conditions: K3PO4, Pd(dppf)Cl2, dioxane/water, heat to ...
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Why is more of a catalyst added, when it is not consumed?

… catalysis, the acceleration of chemical reactions by substances not consumed in the reactions themselves—substances known as catalysts. (Source) Now as I’ve understood, to keep a reaction going, ...
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Does a catalyst increase atom economy?

Somebody I know insists that the use of a catalyst increases the atom economy. They did chemistry at school and were told that a catalyst increases the atom economy. He pointed me to several past ...
George's user avatar
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1 answer
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How does the work that won the 2012 Sustainable Chemistry Award contribute to sustainable chemistry?

I'm seeking a lay explanation for how the work of Dr Marc Taillefer that won the 2012 European Sustainable Chemistry Award, contributes to sustainable chemistry. From the press release, Dr. Taillefer ...
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How exactly does the oxidation of TEMPO by NaOCl/KBr work?

I would like to understand the exact process by which TEMPO is oxidized to the nitrosonium cation by NaOCl, as in the part of the mechanism shown in the diagram (1) surrounded by the red box: The ...
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9 votes
1 answer
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Transition state optimisation on the surface of periclase

I want to model a reaction catalysed by periclase ($\ce{MgO}$) using DFT. I have a good guess on the transition state (TS) of the reaction that goes in gas phase/solvent (produced using MOPAC). The ...
schneiderfelipe's user avatar
9 votes
2 answers
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How can a catalyst not be included in a rate equation if, by definition, it speeds up a chemical reaction?

I thought that anything not in a rate equation was automatically zeroth order and therefore did not affect the reaction. However, I have heard that catalysts can be involved in a reaction while not ...
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3 answers
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How can water catalyse a reaction between iodine and aluminium?

A few drops of water can initiate a reaction between iodine and aluminium. https://www.youtube.com/watch?v=SKSU72-1ERc How can this happen, since iodine is only slightly soluble in water?
Paul Richards's user avatar
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1 answer
11k views

How does a catalyst affect the rate equation?

If I determine the order of the reactants in a reaction without using a catalyst, and then use a catalyst, will the order of the reactants then be different?
user14974's user avatar
8 votes
1 answer
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Catalysist activation energy - the Brønsted-Evans-Polanyi relation

I have stumbled upon something called the Brønsted-Evans-Polanyi relation in a study about the design of catalysts (for reactions like those in hydrocracking fuel production.) The relation shows that ...
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What is an active centre of a catalyst?

I was studying catalytic poisoning and read that in temporary poisoning, the poisoners are held at active centres by weak forces. What is an 'active centre' in this context?
Aakash Kumar's user avatar
8 votes
2 answers
808 views

Why aren't chaperones considered catalysts?

I'm reading about protein folding on Wikipedia and I stumbled on a bit about a class of proteins called chaperones that aid in the folding of proteins by: ...reducing possible unwanted aggregations ...
Melanie Palen's user avatar
8 votes
2 answers
238 views

Regioselectivity in Carbometallation

I am a student of organic chemistry and I frequently watch online open course lectures by various professors around the globe. Of these, in https://www.youtube.com/watch?v=OYAMls5x4EI, at about 27:10, ...
Eashaan Godbole's user avatar
7 votes
4 answers
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How does a catalyst accelerate both forward/reverse reactions simultaneously?

A catalyst is known to speed up both forward/backward reactions of a reversible reaction. But how does this work, because the mechanism for the forward and backward reactions could be different right? ...
daraj's user avatar
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7 votes
2 answers
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Hydrogenation stereochemistry-Pd,Pt, Ni catalysts

When my textbook talks about hydrogenation using Pt, Pd or Ni heterogeneous catalysts, it never mentions if it is anti or syn addition. It simply jumps on to say that for alkynes, NiB2 (P-2) catalysts ...
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7 votes
1 answer
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Ozone catalysis

I know that catalysts don't change chemical equilibrium because they accelerate both the reactions in the same way. I can't understand why CFC catalysts accelerate ozone destruction but not ozone ...
Surfer on the fall's user avatar
7 votes
1 answer
160 views

Multiple "/" in catalysts

What does it mean if a catalyst has multiple "/" symbols, such as $\ce{Mn/Fe/Al2O3}$? Does it mean either $\ce{Mn}$ or $\ce{Fe}$, or does it mean both are supported on $\ce{Al2O3}$?
rmza7's user avatar
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7 votes
2 answers
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Would singlet oxygen in the engine cause a more efficient combustion?

Today someone told me about a new product — a mesh that is made from 5 different metals and when oxygen passes through it, singlet oxygen appears for a short period of time. This mesh needs to be ...
Alexey Dyachenko's user avatar
7 votes
2 answers
14k views

Demonstrating decomposition of hydrogen peroxide using iron(III) nitrate catalyst

I need a way to prove/show that hydrogen peroxide was decomposed through use of catalyst. I want to ensure that my catalyst: $\ce{Fe(NO3)3}$ or iron(III) nitrate is a catalyst, not a reactant/ ...
didgocks's user avatar
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1 answer
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Why is the Jacobsen's catalyst with tert-Butyl groups a better catalyst for epoxidation?

In an experiment I synthesised the below Jacobsen's catalst: I used it to create styrene oxide through epoxidation. Chiral GC analysis showed that the enantiometric excess was lower compared to using ...
Patrick Robertson's user avatar
7 votes
2 answers
245 views

How might ammonia be created in this mechanochemical reaction?

Can mechanical agitation catalyze reactions? It appears so (thanks to Mithoron for the pointer!). We observed the following: We were using 10-micron hBN powder to impact-plate copper bearings (e.g., ...
feetwet's user avatar
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7 votes
2 answers
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Why are hydrogenation reactions exothermic?

I learned that all reactions that yield hydrogen are endothermic (such has reforming) and reactions that use up hydrogen are exothermic (FCC cracking, hydrogenation, etc.). But why is this so? I know ...
mypsilon's user avatar
7 votes
1 answer
2k views

Catalytic iodine in synthesis of phosphonium salts

From Clayden et al. However, iodine is expensive and a way round that problem is to use a catalytic amount of iodide. The next phosphonium salt is formed slowly from benzyl bromide but the ...
Jori's user avatar
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7 votes
1 answer
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Different chemoselectivity of transition metals in catalytic hydrogenation

I am quoting my Clayden et al 2nd edition: Some catalysts are particularly selective towards certain classes of compound – for example, Pt, Rh and Ru will selectively hydrogenate aromatic ...
Mockingbird's user avatar
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7 votes
1 answer
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How can the trityl tetrafluoroborate function as a Lewis-acid catalyst

Trityl tetrafluoroborate is a reagent sometimes used in synthesis as a very mild Lewis acid catalyst, and recently I've been (unsuccessfully) using it in some protecting group chemistry. Several ...
NotEvans.'s user avatar
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7 votes
1 answer
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How can subtilisin still function without its catalytic triad?

I read chapter 9 in the book Biochemistry (5th edition), by Berg, Tymoczko, and Stryer (provided in the NCBI site here). It describes the mechanism of action of the chymotrypsin enzyme. The catalysis ...
Ynk's user avatar
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1 answer
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Why does NaOH catalyze H2O2 decomposition? [duplicate]

I had a lab practice in which I had to test the effectiveness of different catalysts for the decomposition of $\ce{H2O2}$. Among them, there was: $\ce{KI(aq)}$, $\ce{FeCl3(aq)}$, $\ce{MnO(s)}$, $\ce{...
Cristiane Dos Santos Costa's user avatar
7 votes
1 answer
844 views

The Propinquity Effect

I am currently in the process of studying enzyme catalysis and am struggling to get to grips with this concept. As far as I understand, the propinquity effect allows substrates to bind with enzymes in ...
Lucapoli6's user avatar
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7 votes
0 answers
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Why do poisoned catalysts (Lindlar, nickel borate) result in partial hydrogenation of alkynes?

I read that alkene is more reactive than alkyne, so in hydrogenation of alkynes, it's difficult to isolate the alkenes. But with poisoned catalysts like Lindlar's catalyst or Nickel-Boron (Ni2B), they ...
Wang's user avatar
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6 votes
2 answers
792 views

How do I heat my borosilicate reflux column?

I am gonna use a ceramic tape heater, but cannot wrap it around evenly. Is the glass column gonna be okay? I am running some tests on plastic pyrolysis. I am using the reflux condenser to make the ...
Vanadium's user avatar
6 votes
1 answer
6k views

Why do we need acid when making acetone peroxide?

Acetone peroxide is a very dangerous explosive, easily detonated by mild heating, friction or shock. It appears in the form of small white crystals. This compound forms from the mixture of hydrogen ...
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