Questions tagged [elimination]

Questions whose main focus is on E1, E2, E1cb, or any other type of elimination reaction.

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56 views

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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1answer
26 views

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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1answer
54 views

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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340 views

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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382 views

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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77 views

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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1answer
294 views

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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196 views

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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1answer
398 views

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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28 views

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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1answer
72 views

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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235 views

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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290 views

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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4k views

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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1answer
72 views

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 ...
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144 views

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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167 views

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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1answer
9k views

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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2answers
1k views

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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114 views

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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94 views

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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1answer
239 views

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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265 views

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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93 views

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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1answer
414 views

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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1answer
648 views

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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2answers
788 views

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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1k views

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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628 views

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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809 views

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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1k views

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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1k views

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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7k views

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 ...
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678 views

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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393 views

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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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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251 views

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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4k views

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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870 views

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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646 views

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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2k views

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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2answers
6k views

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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288 views

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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2k views

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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1answer
1k views

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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1answer
1k views

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 $...