Questions tagged [elimination]
Questions whose main focus is on E1, E2, E1cb, or any other type of elimination reaction.
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Why are two three-membered rings preferred to a single five-membered ring in the reaction of a dihalide with alcoholic KOH?
The given answer is 1,1-dicyclopropylmethanone:
Step 1 is abstraction of acidic H by the strong base. Then, there's surely going to be anchimeric assistance. But there can be two places where the ...
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Is E1cB possible in the reaction of cyclopentadiene with acetone in presence of ethanolate?
When cyclopentadiene 1 and acetone 2 are reacted with sodium ethoxide in ethanol, what product is obtained? I was told that the correct product 3 is formed by nucleophilic addition of cyclopentadienyl ...
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difference between elimination reactions and oxidation reactions [closed]
I know that oxidation reactions involve the loss of hydrogen. But is the mechanism the same
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Reaction of dihalides with excess of NaNH2
Gem-dihalides react with $\ce{NaNH2}$ to give terminal alkynes. Why is a terminal alkyne prefered?
For example,
I had thought that 2-pentyne would be preferred over 1-pentyne as it would be more ...
user63618
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Cyclic elimination reaction
Which of the following will give cyclic elimination by heating?
phenol
propanoic acid
trimethyl isopropyl ammonium hydroxide
cyclohexyl propanoate
Cyclic elimination by heating is ...
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Reaction of alkyl bromide in presence of piperidine
What are the products of this reaction? I believe there'll be E2 elimination to give the products. Not sure. Help would be greatly appreciated.
The above is the product which I thought might be ...
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0
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Confused about enolate chemistry [closed]
I'm not so sure how this mechanism is supposed to go. Could anyone provide some pointers?
The answer is supposed to be:
In particular, I'm confused about how to break up the two esters.
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What is the major product of bromobutane and sodium ethoxide?
I know that the it is SN2 reaction and $\ce{Br}$ is the leaving group. Second Carbon(from right side) is the beta carbon. As the $\ce{Br}$ group leaves, $\ce{OH}$ will create a bond with one of the ...
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Mechanism for the conversion of dimethyl cyclohexa-1,4-diene-1,2-dicarboxylate to dimethyl benzene-1,3-dicarboxylate using bromine
Question
Convert the first compound into the second using only $\ce{Br2}$
I tried solving it by making a 3-ring with $\ce{Br+}$, and then making one of the oxygens break that ring. Than I used $\ce{...
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Elimination reaction with 1,2-dibromo-4-methylcyclohexane
I was doing a question from a practice exercise on the topic of elimination reactions and alkene synthesis. It is shown below:
I predicted that the product would be 1,2-diiodo-4-methylcyclohexane ...
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Why does the E1cb mechanism proceed in the specific way it does?
We have been learning the E1cB mechanism in organic chemistry, but we have not been delving into the motivation as to why this mechanism occurs instead of others. Consider the following mechanism:
I ...
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How does Hofmann elimination work in this reaction?
In my Chemistry class, we were given this question to solve, and I'm not sure I fully understood the solution.
I understand that since the substrate is bulky, Saytzeff elimination can't happen, so it ...
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Reaction of conjugated alkene with KNH2
I could not think of this reaction fitting into any of the reactions I know except the aryne mechanism. And hence I came up with the following mechanism after seeing the answer (which I've written in ...
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How to tell/control whether sodium ethoxide will react by a substitution or elimination pathway?
Why is the behavior of sodium ethoxide inconsistent?
In a reaction with 1-bromobutane, the anionic part of sodium ethoxide substitutes for $\ce{Br}$:
$$ \ce{CH3CH2CH2CH2Br + C2H5ONa -> ...
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Why does this elimination reaction occur? [closed]
I was confused by why the following elimination reaction hits only one of the hydrogens instead of both isomers that are possible. Please help me out!
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How to decide what pathway a reaction will follow, elimination, addition to a carbonyl or nucleophilic substitution?
There is a substrate such as this,
and it is treated with alcoholic KOH.
I know that a hydrogen in $\alpha$-position to the carbonyl group will be abstracted, leaving a carbanion. My query lies in ...
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Hofmann rule and deviation from E2 mechanism
I've learnt that
The best reaction conditions for synthesis of alkene by dehydrohalogenation are those that promote an E2 mechanism.
(From "Organic Chemistry" by TW Graham Solomons)
But, in the ...
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Which hydrogen does the nucleophile attack in E2 reaction?
This reaction will be both an E2 and SN2, where the E2 will be major and the SN2 minor (If I have done it correctly). I was drawing out the mechanism as I noticed that I was making my nucleophile ...
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How to determine if a reaction proceeds via SN1, SN2, E1 or E2 mechanism?
Give the main product and reaction type: SN1, SN2, E1 , E2.
As the 1-bromohexane is primary and the nucleophile a strong unhindered base, the reaction should be a SN2 reaction. However, the solvent $...
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Conjugated diene t-buOK reaction [duplicate]
Why does the t-buOK abstract the following hydrogen. Doesn't it promote the Hoffman product so it should take the hydrogen from a secondary carbon instead of a tertiary one? Thank you
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Stereochemistry of eliminations similar to E2' elimination
In the E2 reaction, the proton and the leaving group are anti-periplanar typically, so as to attain best overlap of the C-H bonding orbital and C-LG anti-bonding orbital.
In a similar reaction, with ...
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Why is this β hydrogen in trans position to the leaving group?
Problem:
One of the most widely used methods for the formation of $\ce{C=C}$ is β - elimination reaction of the following type:
The spatial arrangement for a bimolecular elimination (E2) of the type ...
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Order of reaction greater than molecularity?
We were taught that the order of a reaction is either less than or equal to it's molecularity. But then I came across a mechanism called E1CB, where the fact was totally reversed. Here molecularity is ...
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Why does the carbocation in this scheme react under elimination conditions rather than being attacked by water?
In the final step of the mechanism, elimination occurs over substitution, why is this?
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Saytzeff and beta elimination [closed]
I am not able to understand the difference between Saytzeff's rule and beta elimination reaction. Also I am writing two reactions below:
\begin{align}
\ce{CH3-CH2-CH(Br)-CH3 + \underset{\text{(...
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Elimination mechanism in alkenes
Do E2 elimination reactions occur in alkenes? If not, what mechanism is used?
If they do, are they limited by any stereochemical rules as alkanes do (antiperiplanar)?
My question is pernitent to the ...
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1
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Does (2-fluoroethyl)benzene undergo elimination via E1cb or E2?
I have seen in two different sources claiming that $\ce{PhCH2CH2F}$ gives styrene $\ce{PhCH=CH2}$ when treated with alcoholic $\ce{KOH}$, but one source suggests an E1cb mechanism, while the other ...
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Why do polarizable nucleophiles favor SN2 over E2?
Weakly basic ions and polarizable bases favor $\mathrm{S_{N}2}$ over $\mathrm{E2}$. Why? The argument used that polarizable nucleophiles form bonds earlier, stabilizing the transition state, can be ...
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What constitutes something being designated as big, bulky in terms of SN2 vs E2
When deciding between $\mathrm{S_N2}$ and $\mathrm{E2}$ for primary and secondary alkyl halides, is there a particular method or molecular size or any other threshold, which allows us to designate ...
5
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Predicting product of amine elimination
From section 'Nitrogen Containing Compounds'
I spent quite a lot of time here but could not figure out the answer. It's not mentioned in my school text book either. The solution given in my book is:
...
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1,2-dibromopropane reaction with OH and NaNH2 [duplicate]
We have the reaction of the alkyl halide $\ce{CH3-CHBr-CH2Br}$ with 1) $\ce{OH-}$ 2) $\ce{NaNH2}$ The answer is propyne.
I am unable to understand why we have performed an elimination reaction here. ...
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What is the major product in the reaction of 2,3-dichlorobutane with sodium amide in liquid ammonia?
I am not able to decide which among 1,3-butadiene and 2-butyne is the major product of this reaction. Will there be even a major product out of the two or will there be a mixture?
According to me, ...
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E1 elimination and alkyne formation
Are E1 elimination reactions possible from a trans dihalide alkane (like 1,2-dibromoethane) all the way to the alkyne (like acetylene)? Or is only E2 possible from the alkene to alkyne? What is the ...
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Use of aqueous KOH and alcoholic KOH in dehydrohalogenation reactions [duplicate]
What is the difference between aqueous KOH and alcoholic KOH? How do they react differently in dehydrohalogenation?
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Why does this E2 reaction occur on the less substituted carbon?
In compound C it eliminates the beta hydrogen attached to the less substituted carbon, rather than attacking the beta hydrogen attached to the tertiary carbon. Why is this the case?
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Why does treatment of a geminal dihalide with sodium amide lead to an alkyne and not an allene?
I've come across the following problem in Klein's Organic Chemistry, 2nd edition:
However, I'm a little bit confused about why the terminal alkyne is produced. I believe that an allene should be ...
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Elimination of HCl from isomeric chlorocyclohexadienes
Which of these is most easily dehydrohalogenated?
a. 5-Chlorocyclohexa-1,3-diene (1)
b. 3-Chlorocyclohexa-1,4-diene (2)
c. 1-Chlorocyclohexa-1,4-diene (3)
d. Both 1 and 3
I encountered this question ...
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Origin of alkenes from Wurtz Reaction
According to Wikipedia:
Also, since the reaction involves free radical species, a side reaction occurs to produce an alkene. This side-reaction becomes more significant when the alkyl halides are ...
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What conditions would make SN1 products the major products over E1 products, and vice versa?
It seems that if a carbocation intermediate is formed through solvolysis, then the product(s) are going to always be a pretty even mix of SN1 and E1 products.
Are there any conditions that greatly ...
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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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What will be the product when 3,4-dibromocyclohexene is reacted with sodium followed by heating with selenium?
I'm tutoring few Class 12 students for their chemistry exams. I'm stuck with few problems. I don't know, if the key is wrong or I am wrong.
According to me product (A) must be the cyclic diene, ...
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