Questions tagged [elimination]

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

35 questions with no upvoted or accepted answers
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E1CB mechanism with replacement of hydrogen step?

In this question by Jay, one of the sub parts of the total question has the following reaction identified as $\ce{E1CB}$ pathway: $$\ce{Ph-CH2-CH2Br} \text{ on treatment with } \ce{C2H5OD/C2H5O-} \\ \...
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When does reaction of alcohol with alumina give ethers and when an alkene?

This problem given in my book confused me a little bit: when an excess of ethyl alcohol vapour is passed over heated alumina ($250^\circ$C), the main product is? I read that this reaction gives an ...
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210 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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1answer
115 views

Does elimination occur when bromonapthalene is reacted with sodium amide in potassium hydroxide?

What should be the product of this reaction? Some books show that an elimination reaction would happen since $\ce{NH2-}$ is a strong enough base to take away a hydrogen on a benzene ring and create a ...
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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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158 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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378 views

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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46 views

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 ...
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34 views

E1 or E2 Elimination? Which Elimination occurs first?

In this reaction scheme, two dehydrobrominations occur. A bulky base is used but both hydrogens are sterically hindered. How is it possible to determine, which one is removed first? Or is this an $E_1$...
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How is elimination reaction (E1) possible without base and in presence of acid?

When learning about E1 we were taught that three things are important factors to judge if the reaction is E1 or E2 Substrate ( 3,2,1 favours E2 but only 3 favours E1 ) Base ( Stronger Base favours E2 ...
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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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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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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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Evaluating inductive effects in cyclic compounds

I was required to find the products on heating the hydroxide of; Now it's easy enough to find the answer; Hoffman elimination isn't going to happen from the methyl, and the n-propyl doesn't have $\...
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1answer
56 views

On the relative ease of E2 dehydration

Concerning alcohol dehydration, I get that it's E1 in secondary and tertiary alcohols, that it's E2 in primary alcohols, and also why E1 reaction is easier for tertiary alcohols as compared to ...
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44 views

Confusion regarding dehydration of 1° alcohols

My lecturer told me that 2° and 3° alcohols prefer to dehydrate through E-1 mechanism. On the other hand, 1° alcohols tend to prefer the E-2 mechanism, which does not involve the formation of a ...
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31 views

Which is more reactive in E1, benzyl or allyl

I'm don't know the english terminology for chemistry so sorry for probably butchering some terms. My question is, which of these is more reactive in an E1 reaction: The bottom two are the ...
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76 views

Dehalogenation of vicinal dihalo alkanes

Which mechanism will the following reaction follow? Will it follow E2 mechanism? If yes, then how would 2,3-dibromobutane undergo this reaction? Does it form both cis and trans butene or is the ...
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60 views

Which mechanism would be followed by a certain reaction with good leaving group?

In my class test, I was asked this question: Which mechanism would be followed by a certain reaction with good leaving group? E1 reaction E2 reaction No reaction both E1 and E2 I answered 4 ...
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79 views

Find the major products when these cyclohexenone bromides react with caustic potash in alcoholic medium:

Question: Also find the order of the rates of the given reactions. Answer: The answer of this question is given as option 'D' ie. all products are identical, however I am getting the answer as ...
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142 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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93 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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47 views

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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1answer
243 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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29 views

Can methoxide ion be used as a base in an E1 elimination reaction?

This one problem given in my textbook is confusing because all I know is we can use a weak base for an E1 Reaction. But the reagent given is a methoxide ion. I thought the answer would B but it is C. ...
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What to do when different conditions favor different substitution and elimination reactions?

How do I know which product will occur when different conditions which favors different reactions are all together? For example: Let's say that I have a secondary substrate (which doesn't favor ...
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119 views

Elimination vs reduction reactions - how to tell

Here are two compounds: Compound H: and compound I: Compound H reactions with the reagent shown below to form compound I and two other products. How would you clarify this reaction? I thought it was ...
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Finkelstein reaction of vicinal dihalides

I recently came across the following in my OChem class: Ethylene dichloride on reaction with NaI in acetone reacts via E2 mechanism to give ethene. I have three questions: Since it is an E2 ...
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171 views

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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29 views

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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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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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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279 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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227 views

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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8k views

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 ...