Questions tagged [elimination]
Questions whose main focus is on E1, E2, E1cb, or any other type of elimination reaction.
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How would the mechanism for this reaction look like?
For the first part, I belive that the molecule is just deprotonated by the base which allows for the Br to be eliminated as the proton that is removed is antiperiplanar (E2) which would mean that the ...
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Why does alpha-carbon substituents increase the rate of E2 reactions?
The reason for more reactivity of more substituted alkyl halides for E2 Reaction is said to be due to the more stability of its more substituted alkene character having transition state but here (...
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Substitution or elimination when a chloroalkene reacts with NaOH in ethanol?
NaOH + EtOH will eliminate the Cl atom forming a double bond. At least, that's what I think. 3 could also be a viable answer since the OH can also attack the said double bond (this is probably not ...
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Why can't ethoxide ion act as nucleophile?
Consider the reaction of chlorocyclohexane with ethoxide in a suitable inert solvent. The major product according to my textbook is cyclohexene, which implies E2 reaction pathway. Why not SN2?
$\ce{...
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Enamine formation mechanism. Can't there be alternatives?
I'm studying organic chemistry, more specifically the imines and enamines. I've read about the mechanism of formation of enamine from a generic ketone and a question popped up in my mind. The ...
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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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how does enolate affect an elimination reaction?
From my class:
But why wouldn't the reaction proceed through this way, which makes more sense? Since the reaction above generates an enolate bearing a negative charge first, making the molecule less ...
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Which substrates will undergo an E2 reaction to give a (Z) alkene?
What I do know: E2 reactions are concerted and have an anti-coplanar transition state, where the leaving group and the hydrogen being abstracted have a dihedral angle of 180 degrees.
What I don't ...
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NaOt-Bu + chloroethane
What is the major product formed by reaction of sodium tert-butoxide and chloroethane?
I thought NaOt-Bu is a bulky base and the major product will be ethene due to E2. But the answer says t-butyl ...
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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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Which 1,2-methylene shift is more favourable in ring expansions where ring has substituents
In the above reaction, first the -OH group is protonated after which it leaves creating a carbocation intermediate as shown
Now, ring expansion is a more favourable rearrangement, however there is a ...
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Why will a lone pair from H2O not attack a C+ atom in elimination reaction?
In step three of reaction between H2SO4 and alcohol, why will the H2O attack the H atom instead of the C+ atom? they both have positive charge and in nucleophilic substitution reactions the c+ atom is ...
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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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When does reaction of alcohol with alumina give an ether and when an alkene?
What is the main product when an excess of ethyl alcohol vapour is passed over heated alumina at 250 °C?
I read that this reaction gives an ether (here, diethyl ether) at relatively lower temperature ...
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What would be the product(s) when 2-iodobutane is heated with tertiary butoxide?
The following question from Black Book Organic Chemistry IIT JEE Advanced Level Papers [1]:
Choose the correct option(s) among the following about [P]:
A) Two C−H bonds in [P] are involved in ...
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Does E1 mechanism always imply first order reaction?
Oxford University Press, Okuyama & Maskill: Organic Chemistry — Chapter 13: Multiple Choice Questions, Question 1:
Which of the following statements regarding the E1 mechanism is wrong?
a) ...
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Does E1cB take place over here?
I formed this product (reason: alkene has 6 alpha hydrogens)
---->
However, it turns out, this is the answer:
The reason why I suspect this is e1cb is because NO2 could stabilize the carboanion (...
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What kind of rearrangement happens between 2,2,5-trimethylcyclopentanol and concentrated sulfuric acid?
Question:
My attempt:
After getting the carbocation after protonation, in order to form a more stable alkene, it rearranged the methyl group on the adjacent carbon so as to get the alkene in the ...
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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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Reactivity of 1-bromo-4-tert-butylcyclohexane isomers with methanol
(1s,4s)-1-bromo-4-tert-butylcyclohexane (1) and (1r,4r)-1-bromo-4-tert-butylcyclohexane (2) are heated (E2) with $\ce{NaOCH3}/\ce{CH3OH}.$ Which isomer will react faster?
What will change when $\ce{...
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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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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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Difference between SN' and elimination reactions
My professor has recently taught us about SN' reaction example in which 3-bromo-3-methyl-but-1-ene was reacted with with KCN to yield 4-methyl-pent-3-ene-nitrile as the major product.When I asked him ...
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Why is the major product of an elimination reaction an alkyne and not the diene?
1,2-Dibromopropane and KOH react together to form propyne. But I wondered if 1,2-propadiene was also being produced since the there is also a proton on the $\ce{CH3}$ group to be used in the ...
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Mechanism of this addition-elimination process
In Part 1 of the synthesis of Maoecrystal V (found on synarchive), the last step subjects a $\ce {\alpha, \beta}$-unsaturated ketone to $\ce {I2}$ and pyridine, as shown below:
I am wondering what is ...
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Conversion of cyclohepta-1,3-diene to cyclohepta-1,3,5-triene
In the landmark synthesis of tropinone by Willstatter in 1901, an interesting step involves the use of $\ce {Br_2}$, quinoline to convert cyclohexa-1,3-diene to cyclohexa-1,3,5-triene. In the scheme ...
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Why do active methylene compounds give Sn2 reactions?
I dont understand why they are strong nucleophiles when the negative charge is resonance stabilised. Also it is bulky, is there any chance of elimination?
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Reaction of aqueous KOH and alcoholic KOH with alkyl halide [duplicate]
CONTEXT:
Here's reaction of alkyl halide with aqueous $\ce{KOH}$
and here's the reaction for dehydrohalogenation by alcoholic $\ce{KOH}$
Question
Initially $\ce{KOH}$ is aqueous. On reacting with ...
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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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Mechanism of acid-catalyzed ring opening of a cyclopropane ring
I have a question regarding following synthesis which apparently only needs a sour medium to occur:
What exactly happens as a mechanism? What I thought was: The alcohol group gets protonated and ...
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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 ...
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Elimination reaction mechanism decision (order = 1 or 2)
Match the following:
\begin{array}{}
& \textbf{Column I}&&\textbf{Column II} \\
\text{(A)} & \ce{CH3-CHBr-CD3} \text{ on treatment with alc. KOH gives}& \text{(P)}& \text{E1 ...
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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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Mechanism of reaction of ketones with isoalkanes under conc. sulfuric acid and heat
Taken from the book of GOC by Dr. O.P Tandon, Himanshu Pandey, Dr. A.K. Virmani,
Can anyone elaborate on the mechanism?
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Does Ei or pyrolytic elimination reaction undergo carbocation rearrangement?
I've read about E1 reaction (unimolecular elimination reaction) which forms the most stable carbocation first and then undergoes the elimination.
Ei is also mentioned to be "unimolecular" in ...
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When is Zaitsev product formed in pyrolytic elimination reaction?
I recently came across a problem of choosing which product to be made in case of pyrolytic elimination reactions. I was taught that usually Hoffman products are formed in such reactions. For e.g.:
In ...
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Determining if the product would be cis or trans after an anti elimination on fischer projections
I find these kind of problems really confusing for some reason, but I saw a way on the web and tried doing it that way:
I considered the basic Fischer operations (Vertical: Below the plane of paper, ...
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Can dehalogenation reaction occur through E2 mechanism? [closed]
I have seen examples of dehydrohalogenation reaction that occur through E2 mechanism but never came across dehalogenation reaction that occur through E2 mechanism (for example, dehalogenation of 1,2-...
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Which of the given compound has the highest rate of dehydration?
I came across this question recently:
For which compound acid catalyzed dehydration rate is highest?
Now, they all are secondary alcohols so their dehydration should follow E1 mechanism and the ...
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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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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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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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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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Decarboxylation of 2‐cyano‐2‐cyclohexylideneacetic acid [closed]
2‐Cyano‐2‐cyclohexylideneacetic acid (1) is heated and $\ce{CO2}$ is lost:
[
Why is this not formed?
In other words, why do π-electrons move into the ring?
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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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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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Equilibrium with an E2 step
E2 mechanisms are known to be irreversible in general, because the forward step takes 2 species and produces three species, and a trimolecular reverse step is unlikely, purely on entropic grounds. (As ...
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Major product in dehydration of alcohol
Consider the dehydration of the following molecule with conc. $\ce{H2SO4}$ at $443 \text K$:
The possible products are:
The first one is the Zaitsev product and the second one Hofmann product.
...
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Determine mechanism: E1 vs. E2
I am asked to indicate what is the product of this reaction, and the mechanism by which it is formed:
3-Bromo-3-ethylpentane + sodium hydroxide in methanol, 50 ºC
I identify it as an elimination ...
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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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