Questions tagged [elimination]
Questions whose main focus is on E1, E2, E1cb, or any other type of elimination reaction.
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Phenethylhydrazone decomposition mechanism
I was going through a problem in the book Advanced problems in organic chemistry by Chouhan:
I figured out that since di-isopropyl amide will act as a hindered base it will take out the following ...
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Order of rate of acid catalysed dehydration of alcohols
The relative rate of acid catalysed dehydration of following alcohols would be:
According to me, we have to arrange them in order of their carbocation stability.
Q will be the most stable as it is ...
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Factors affecting rate of β-elimination reaction with alcoholic KOH
The question asks for the rate of reaction in $\beta$-elimination using alcoholic $\ce{KOH}$.
Arrange the following alkyl halides in decreasing order of rate of $\beta$-elimination reaction with ...
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Recognising a rate-determining step in E1
If there is a hydride/methyl shift possible in E1, then is the carbocation formation the rate-determining step (RDS), or the shift, or is it considered a cumulative step and happens all at once?
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Rate of dehydration of alcohols having keto group
The following question was asked in IITJEE-Screening 2000,
Which of the following will be most readily dehydrated in acidic conditions?
I thought that the answer would simply be (c), as its ...
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Stability of carbocations with -M groups in beta position
First part
The original question was to arrange the following compounds in the order of their rate of dehydration with conc. $\ce{H2SO4}$:-
(A) $\ce{CH3-CH(OH)-CH2-CH=O}$
(B) $\ce{CH3-CH(OH)-CH2-C(=O)...
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Role of alcoholic potassium hydroxide in an E2 reaction
Which of the following compound will give least substituted alkene as major product with alcoholic $\ce{KOH}$.
The options are:
1.
2.
3.
4.
I am confused between options 1 and 3. Both seem to give ...
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Dehydration of primary alcohols without a β-hydrogen
What happens in dehydrations of primary alcohols (in presence of acid catalyst at high temperatures) which don't have a β-hydrogen?
For example, in the case of neopentyl alcohol, will it dehydrate as ...
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What happens on heating an ester?
While solving a few questions a came across a problem which asked me what would happen when sec-butyl ethanoate was heated.
I had never read about this reaction before and took to researching through ...
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Temperature required for E1 elimination reaction
I wanted to ask what's the temperature required for carrying out elimination reactions?
Wherever I read about elimination reactions, they just mention that elimination reactions occur at high ...
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Which will be major and minor alkene formed if E1 reaction occurs on 2-chloro-2,4,4-trimethylpentane?
More substituted alkene should be major product while the less substituted as minor product as it is E1 mechanism.
But in my answer sheet it is given reverse, i.e. major as less substituted and minor ...
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Is the elimination reaction between 1 1 dibromo cyclopropane and phenyl lithium feasible in alkaline medium (and some heat)
I found this question in one of my question papers for the JEE ,
My sir gave me an explanation that due to resonance between lone pairs of the bromide and π bond formed.
This reasoning doesn't seem ...
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Substitution and Elimination Reactions
Why strong bases only give elimination products as major while they could give substitution products too being good nucleophiles? (I am excluding those non nucleophilic bases)
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Why can alcohol undergo elimination just by sulphuric acid?
In both $\mathrm{E1}$ and $\mathrm{E2}$ reactions with alcohol, loss of a leaving group and proton transfer are required. And proton transfer requires a base to get that hydrogen in alcohol.
I know ...
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Conversion of methylcyclopentanol to cyclopentanone
How to convert methylcyclopentanol to cyclopentanone?
I tried eliminating the alcohol group as $\ce{H2O},$ but that gives Saytzeff product. If only I can get the Hofmann product (methylene ...
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Does SN2 favor strong nucleophile and SN1 favor weak nucleophile? Does E2 favor a strong base, and E1 favor a weak base?
I understand if you have a protic solvent, it will stabilize the strong base (to form weak acid) or the strong nucleophile. The protons would react with them. To have an SN2 or an E2, so you need an ...
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Why can SN2 reactions occur when the reagents are a primary substrate and a weak nucleophile/base?
The reagents are ethyl bromide and water. In this Khan Academy video at 5:20, the narrator says because ethyl bromide is a primary substrate, the reaction is neither SN1 or E1. This makes sense ...
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What are the organic reactions that are taking place in this reaction?
I know that A is the product of a Knoevenagel condensation between the aldehyde and the diethyl malonate, due to the acidic protons of the latter, but I don't know what the reaction between that ...
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What would be the product of following elimination reaction?
Question
Doubt
The answer is given B. But why cant it be C after all formation of cyclopropane would increase angle strain?
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In the following reaction is E2 or Sn2 favorable?
Question
Doubt
It is quite obvious that carbonyl compound is going to convert into alkane, but what confuses me is whether Sn2 or E2 will occur at bromide position
Although there is heating( which ...
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Comparing between nucleophilic and basic strength of acetylene ion [closed]
Question
In this question I understand that 2 reactions- Substitution and elimination- will occur. But which will be major?
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Which elimination is this?
This is the question:
$$\ce{Cl-CH2-CH2(Cl)2->[alc KOH][Δ]?}$$
Now, I got the answer right but I think that the reaction should go by the $\ce{E1}$ mechanism because of the high temperature/heat, ...
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Comparing between SN2 and E2
Question
I am confused between the questions B. And C. The earlier is SN2 and later is E2. But what makes the difference?
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Elimination of bromine with sodium iodide and electrocyclization
I've been trying to solve the following reaction scheme for a while now and I am having trouble especially with the products E and F.
For product D I got the following, but I'm unsure about ...
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What will be the major product of the following dehydrohalogenation?
Question:-
My Attempt:-
I believe the answer should be C, because even if 2-butyne is formed $\ce{NaNH2}$ should cause it to rearrange into a terminal alkyne. Hence the answer should be 1-butyne. ...
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Can ring inversion in Cis-Decalin allow the E2 reaction?
This is a tutorial question I need to do, I initially thought the question was testing whether students properly understand (1) chair conformations of decalin, and (2) that the leaving group and the ...
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why are E2 and SN2 reactions not competing reactions?
I am quite confused about the competition of $\mathrm{E2}$ and $\mathrm{S_N2}$ reactions. My lecturers say $\mathrm{E2}$ and $\mathrm{S_N2}$ reactions are not competing reactions but most websites say ...
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Reaction of alc. KOH with alkyl halide
The following question was given in FIITJEE study material:
At first, I thought it should be elimination. But, soon I realized that there is no heating, plus a primary alkyl halide is used. So, "...
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E2 towards secondary over tertiary and primary beta-carbons
I would like to convert this tertiary bromoalkane to this trisubstituted alkene via E2
Theoretically, using a strong base (NaOH) would result in the formation of the Zaistev product (tetrasubstituted)...
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Grammar of elimination reactions
I would like to double check the English grammar of a sentence of an elimination reaction, but I cannot find an answer.
I'd normally say "the elimination of A with X as the leaving group", where A is ...
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Hofmann and Zaitsev products
It is known that, with regard to the elimination reaction, the Zaitsev product is the thermodynamically more stable product, which is also often the more substituted alkene while the Hofmann product ...
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Why does SN1 not occur as a minor product when a strong nucleophile/strong base attacks a tertiary substrate?
The following is part of a table that appears in my Organic Chem Text (Klein)
Nucleophile Only (e.g. Strong Nucleophile/ Weak base)
$1^\circ - \text{ SN2}\\
2^\circ - \text{ SN1 + SN2}\\ 3^\circ - \...
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Why do polar aprotic solvents favour SN2 over E2?
I was reading about Substitution and Elimination Reactions and I came across the following on MasterOrganicChemistry:
Polar protic solvents tend to favor elimination (E2) over substitution (SN2). ...
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How were the Hoffman's and the Zaitsev's rule formulated even before the discovery of the electron?
I recently studied Zaitsev's and Hoffman's rules for deciding which product is formed via elimination and noticed that the rules for formulated much before the discovery of electrons and any ...
user78585
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Kinetics for E1cb reactions
We were taught that the kinetics of a reaction is determined by the reactions ‘rate determining step’ which is also the slowest step of the reaction. For E1 as well as E2 reactions the slowest steps ...
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Chugaev and Selenoxide Elimination giving different products
In class we are going over intramolecular elimination. In this question I will provide two similar reactants that provide a different mixture of products.
The chugaev elimination gives a 50/50 ...
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Why does d/l-2,3-dibromobutane on reaction with NaI/acetone give cis-2-butene?
This is what I have read/know about the dehalogenation of vicinal dihalides by NaI/acetone:
The two halides which are leaving must be on opposite sides (from the mechanism).
In case they are present ...
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Reactivity of primary and tertiary alkyl halides
From USNCO 2004, Q58:
The reaction between which pair of reactants occurs the fastest for $[\ce{OH-}] = \pu{0.010 M}$?
(A) $\ce{CH3CH2CH2CH2Cl + OH-}$
(B) $\ce{(CH3)3CCl + OH-}$
(C) $...
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Quaternary Ammonium salts and peroxy acid
I came across this question in my test:
This compound
is treated with $\ce{CH_3CH_2I}$ and then with $\ce{H_2SO_5}$ and heated.
The product is:
A)
B)
$\ce{CH_2CH_2}$
...
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Number of products on dehydrobromination
Question:
The total number of alkene products possible from the dehydrobromination of 3-bromo-3-cyclopentylhexane using alcohol KOH is :
This question was asked here before but I am getting more ...
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Can't decide between E1 and E2 mechanisms for this reaction
I can see that due to the substrate being bulky, an elimination reaction will take place and not substitution. The reagent is a strong base. E1 reactions are independent of the base chosen, and E2 ...
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Where will the positive charge shift in the E1 mechanism of dehydration of an alcohol? [closed]
My Attempt: according to me the double bond should be in position no. 2 but the correct answer has a double bond in position no.1. Why is it so?
Thanks in advance.
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Elimination reactions of vicinal dibromide
When a vicinal dibromide undergoes elimination reactions in vigorous basic conditions, say in ammonia with $\ce {NaNH2}$, is the product an alkyne or is it a conjugated diene? I would think that the ...
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Please explain the reason why E2 mechanism occurs
I known as that when the weak bases are reacting with 2° alcohol, E1 mechanism occurs. But, in the picture, E2 mechanism is occurred. Why E2 mechanism occurred?
In step [3]
Weak base : pyridine
Did ...
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Do bulky bases participate in substitution reactions?
I see how bulky bases influence the regioselectivity of E2 and E1 reactions. I do not see very much content on the involvement of bulky bases in substitution reactions.
I know that bulky bases like t-...
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Why do *tert*-butyl ethers in diluted sulfuric acid undergo elimation instead of solvolysis?
My organic textbook states the pathway for propyl tert-butyl ether in dilute sulfuric acid will follow E1 with a tertiary carbocation intermediate. It mentions that Sn1 will only occur with good ...
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Can vicinal dihalide produce conjugated alkene in strong base?
In Klein's Organic Chemistry (3rd edition), p. 410, we learn that vicinal dihalide can produce alkyne in strong base. And on Reaxys I see many reactions of this sort. For example:
However, why isn't ...
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Rearrangement with sodium iodide (ring opening)
I'm not able to figure out the mechanism for this reaction. I don't see how sodium iodide in acetone could lead to rearrangement, and surprisingly ring opening!
What is this reaction called, if it ...
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Multiple leaving groups and SN2/E2
In the first stage of the reaction i am confused in which place will the SN2 happen (we have aprotic polar solvent and 4 leaving groups). In my opinion SN2 will happen either to the carbon with F- ...
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When does a pinacol undergo dehydration or rearrangement?
What happens when the above pinacol is treated with -
(a) conc. sulphuric acid
(b) dil. sulphuric acid
I'm confused between pinacol rearrangement and dehydration (E1 or E2?), as both possibilities ...
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