Questions tagged [reaction-mechanism]
The detailed (and as complete as possible) description of plausible or observable pathways leading from reactants to products of a chemical process. This tag should be applied to questions about these processes. It may be applied to hypothetical and/or proposed mechanisms.
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How do organic chemistry mechanisms become accepted?
Now I have been learning chemistry for five years. I remember when I started organic chemistry, it was fun to draw arrows between molecules to show, as if in a mathematical demonstration, how the ...
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How does Walter White make pure crystal meth using a non-stereospecific reaction?
In the highly-rated TV series, Breaking Bad, Walter White, a high school chemistry teacher recently diagnosed with cancer, takes to making the illicit drug, crystal meth (methamphetamine), by two main ...
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Regioselectivity of acid-catalyzed ring-opening of epoxides
Not to be confused with what is the mechanism of acid-catalyzed ring opening of epoxides.
What is the correct order of regioselectivity of acid-catalyzed ring-opening of epoxides: $3^\circ$ > $2^\...
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Mechanism of arene side chain oxidation by permanganate
When treated with hot, concentrated acidic $\ce{KMnO4}$, arenes are oxidised to the corresponding carboxylic acids. For example, toluene is oxidised to benzoic acid.
I've tried to examine how this ...
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Why does alcoholic KOH prefer elimination whereas aqueous KOH prefers substitution?
What is the basic difference between aqueous and alcoholic $\ce{KOH}$? Why does alcoholic $\ce{KOH}$ prefer elimination whereas aqueous $\ce{KOH}$ prefers substitution?
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Why does CaCO3 react with HCl, but not with H2SO4?
I have a wonderful reaction of marble chips, $\ce{CaCO3}$, with hydrochloric acid, $\ce{HCl}$, and carbon dioxide was released beautifully (fast, large volume, easy to measure and makes good visual ...
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How does ammonium nitrate explode on its own?
I thought ammonium nitrate was an oxidizer that needed to be mixed with fuel to form a high explosive (e.g., ANFO). But apparently there have been accidental explosions involving just the "...
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What exactly is happening when sodium, potassium, or other alkali metal explodes in water?
There are lots of videos on YouTube showing sodium, potassium, etc. exploding when dropped into water (this, for example).
I understand that when an alkali metal is exposed to water, a violent ...
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Why super glue does not stick inside their own bottle?
We usually use super glue to stick any two objects but I was wondering like why don't they stick inside their own bottle ?
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Stereoselectivity of dihydroxylation with osmium tetroxide
Dihydroxylation responds to steric effects and proceeds at less hindered positions. What will be the major product in the following reaction if the reagent used is $\ce{OsO4}$ followed by $\ce{NaHSO3}$...
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Unusual Friedel–Crafts alkylation with pivaloyl chloride
In class we were told of an anomalous Friedel–Crafts reaction with a tertiary acid chloride — $\ce{(CH3)3CCOCl}$, or pivaloyl chloride. When this reacts with benzene in the presence of $\ce{AlCl3}$, ...
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What is the role of pH in azo coupling reaction of diazonium with phenol and aniline?
Why is it so that azo coupling with phenol needs basic pH (9–10) and with aniline it needs acidic pH (4–5). How does pH participate in the mechanism? I have searched the internet for quite a while ...
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Why are solids and liquids not included in the equilibrium constant? What about in a reaction rate calculation?
Take for instance the reaction
$$\ce{H2(g) + I2(s) <=> 2HI(g)}$$
The equilibrium constant would not include the solid $\ce{I2}$, but why is this? I have read that its concentration is a ...
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Why does the unstabilised Wittig reaction selectively form cis alkenes?
This question is meant for a simple unstabilised ylide.
The mechanism of the Wittig reaction, as given on ChemTube3d, involves a concerted formation of the oxaphosphetane (this is generally favoured ...
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Why does hyperconjugation help for ring cleavage?
The question was to rationalize it the ring cleavage happens concerted or non-concerted.
The papers "The Mechanism of the Thermal Decomposition of
1-Pyrazolines and Its Relationship to
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Selective nitro reduction of poly nitro compounds
Is there any way through which I could selectively reduce one $\ce{NO2}$ group from a dinitro- or trinitro- compound to an amine.
I was reading Solomons and Frhyle and it says that m-dinitrobenzene ...
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Which compound reacts faster in the Cannizzaro Reaction?
Which reacts faster in the Cannizzaro Reaction?
a) $\ce{OHC-C6H4-NO2}$
b) $\ce{OHC-C6H4-OCH3}$
Obviously, a better hydride releasing group will react faster. Therefore my answer was b, as $\ce{-...
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Addition of hydrogen bromide to 1,3-butadiene: thermodynamic and kinetic control
The reaction of one equivalent of hydrogen bromide with 1,3-butadiene gives different products at under different conditions:1
The addition of hydrogen chloride also gives rise to similar products.2 ...
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Thermodynamic vs Kinetic Sulphonation of Naphthalene
The left hand isomer is clearly the kinetically favoured product and the right hand isomer is the thermodynamically favoured product. However, I have no idea why. Can you explain?
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Products of Reimer–Tiemann reaction of 4-methylphenol
p-cresol (4-methylphenol), undergoes the Reimer–Tiemann reaction upon treatment with chloroform ($\ce{CHCl3}$) in alkaline medium. Which of the following is the major and minor product?
A. 2-...
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Can magnetic fields affect a chemical reaction?
This question was asked recently in an interview and I just said that "Yeah, like if the reaction involves ions or paramagnetic species". But the interviewer went on and asked me to elaborate on HOW ...
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Reaction of alcohols with PCl5 and PCl3
The reaction of alcohols $\ce{ ROH }$ with $\ce{ PCl5 }$ and $\ce{ PCl3 }$ yields an alkyl halide $\ce{RCl}.$ With $\ce{ PCl5 }$, the reaction is quite simple leading to the formation of $\ce{ RCl }$ ...
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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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What happens to a molecule while it is reacting?
I recently learned about the graph of activation energy that looks like this (source):
I was wondering, what actually happens to the reactants as time passes on the graph? If we were to look at the ...
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Why do we get slightly more inversion product than retention product in SN1 reaction?
Theoretically, in $\mathrm{S_N1}$ reaction we should get a racemic mixture as the product because the nucleophile can attack from either side of the formed carbocation.
However, many textbooks claim ...
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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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What makes diazo compounds so unstable and explosive?
I once had an Orgo TA refer to a diazo compound as "diazo-boom-boom" (the technical term). I have always been curious as to the reason behind the instability and reactivity.
According to Wikipedia
...
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Why doesn't the SeO2 oxidation of ketones stop at the hydroxyketone stage?
When $\ce{SeO2}$ is used to oxidise aldehydes and ketones, $\ce{SeO2}$ becomes hydrated in water, and the active reagent is selenous acid $\ce{H2SeO3}$ which oxidizes aldehydes and ketones to furnish ...
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Which is the currently accepted mechanism of a Wittig reaction?
The Wittig reaction is one of the most significant advances in synthetic organic chemistry in the 20th century and rightfully won its discoverer, Georg Wittig, the Nobel Prize in Chemistry.
A Wittig ...
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What is the role of sulfuric acid and mercury(II) sulfate in the oxymercuration of alkynes?
I have a homework problem where I'm given a terminal alkyne. The goal of the problem is to choose the reagent that will result in a particular ketone.
Here's a really general view of the reaction I ...
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The acidity of boric acid
The “real way” boric acid behaves as an acid in water is first by acting as a Lewis acid (bottom reaction, in black). In fairness to the undergrads, I’d bet >25% of graduate students around the ...
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Why does a mixture of siloxene and cerium(IV) sulfate luminesce?
I performed an experiment where siloxene and cerium(IV) sulphate were mixed together: when I did so the mixture produced an orange-yellow glow. Why does it glow? What is it about the two chemicals in ...
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HI/P reduction mechanism
I recently answered a question about Breaking Bad's initial methamphetamine production method (i.e. the reduction of (pseudo)ephedrine). The reaction is as follows:
(Source)
It is infamously known ...
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Why do SN2 reactions of alkyl halides proceed differently with KCN and AgCN?
Alkyl halides react with $\ce{KCN}$ to form alkyl cyanides as the main product, whereas the use of $\ce{AgCN}$ leads to isocyanides as the chief product. Why does this happen?
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How to relate a reaction barrier to the time the reaction needs to proceed?
As I am writing this I am at a conference and one of the participants just asked a question where he linked reaction barriers to durations for the reaction to complete. To paraphrase:
From our ...
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Iron chemistry: acetates for ebonizing wood
I have recently been “brewing” what is commonly called “iron acetate” for ebonizing wood, and I'd like to understand the chemistry of the iron/acetic acid reaction, which should be fairly simple, but ...
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Do Cyclohexane-1,3-diones Give Positive Haloform Reactions?
Recently a post appeared on ChemSE asking why cyclohexane-1,3-dione (dihydroresorcinol) 1a doesn’t give a positive iodoform test. Unfortunately, the post was subsequently taken down after several ...
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Migratory aptitude in Baeyer-Villiger reaction
In short, I do not understand how or why the migratory aptitude is as listed in every textbook I've read.
Firstly, they talk about a positive charge being built up that is stabilised by the movement ...
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What is the mechanism of the reaction between hexane-2,5-dione and nitrous acid?
I don't understand the mechanism of the first reaction; I tried different ways but I can usually find how to make the ring without the double bonds, but it's obviously not the right thing; I think ...
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Addition of HOBr across C=C
Source: Carey Advanced Organic Chemistry B, problem 4.1 b
Looking for interesting problems about addition to C=C, I came across this in the back of Carey. It looks like a simple addition across ...
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Ipso substitution and its rules
I was taught that the following reaction happens:
It is called the "ipso-substitution". My professor had told me that it occurs in the case of $\ce{-SO3H}$ and $\ce{-COOH}$. But he had ended the ...
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Reduction of carboxylic acids by LiAlH4
I've read that when a carboxylic acid reacts with $\ce{LiAlH4}$ the corresponding alcohol is formed:
But when I try to think of the mechanism, I get stuck here:
$\ce{LiAlH4}$ produces $\ce{H-}$. ...
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How do the molecules know the future? How do they proceed to form "Most Stable" compound?
I'm tutoring few students for Chemistry. During the course, I many times use the phrase "Out of these possibilities this one is stable. So it is formed". I get questions like, "How do the molecules ...
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Can in any case the faster step of the reaction be rate determining?
I found a sentence in book which states the reverse step of this reaction ( I forgot what was it!) has the faster step as rate determining .
Even Rate determining step-Wikipedia states:
In ...
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ICHO Synthesis Problem 2018
I've several doubts about this ICHO synthesis problem, which was a part of the preparatory problem package of 2018 (so yes, it's not a part of an ongoing contest)
Before sharing the answer given, I'...
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Are compounds containing active methylene groups positive for the haloform test?
Are compounds containing active methylene groups (e.g. 1,3-diketones) positive for the haloform test? Support your answer with a suitable explanation.
I was stuck on a certain question wherein a ...
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Why is the rate of reaction of polar EAS favored by inductive effects and the rate of less polar EAS reactions through hyperconjugation?
1. Reactions involving strong electrophiles (nitration) are
said to be governed
by
Inductive effects thus the order of nitration is
D>C>...
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If SOCl2 reacts with alcohols via SNi, why doesn't POCl3?
A bit of a follow-up to Why is thionyl chloride preferred for preparing alkyl chlorides from alcohols?.
The reaction with $\ce{SOCl2}$ is also used instead of $\ce{PCl3}$ and $\ce{PCl5}$ when ...
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Carbometalation of alkenes
Alkynes are capable of undergoing carbometalation, e.g. with organocopper reagents:
Why don't the corresponding alkenes undergo analogous carbometalation reactions? Is β-elimination the issue?
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Designing a theoretical synthesis of methamphetamine from phenylpropyne
I am asked to synthesize "methamphetamine." Note that there is no configuration designated for this molecule, and methamphetamine refers to a very specific configuration. In any case, here are the ...
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