Questions tagged [rearrangements]

For questions about specific rearrangements within organic chemistry.

Filter by
Sorted by
Tagged with
3 votes
0 answers
70 views

Acidification of a vicinal diol [duplicate]

The following is a question from Advanced problems in organic chemistry by MS Chouhan: The options given are: My initial thought was that this could be a pinacol–pinacolone rearrangement. However ...
user avatar
0 votes
0 answers
39 views

General conditions for aryl migration of 2-bromo-1,1-diphenylethylene with sodium amide [duplicate]

In this reaction, I am quite unsure whether a phenyl shift would be involved or not because I was managed to solve the phenyl shift mechanism before in pinacol-pinacolone rearrangement. What are the ...
user avatar
  • 1
-5 votes
1 answer
45 views

Mechanism of terpene alcohol rearrangement [closed]

I thought about all kinds of hydride shifts that could be possible here, but I still could not figure out how the mechanism would work.
user avatar
2 votes
4 answers
142 views

Hydride shift or Methyl shift

For the carbocation (A) given in the reaction, first we can rearrange it by ring expansion (4 to 5) then we have two choices either H-shift or methyl-shift. My teacher told me that Hydrogen is the ...
user avatar
  • 137
0 votes
0 answers
26 views

Why doesn't picolinamide undergo Hofmann rearrangement to form 2-aminopyridine? [duplicate]

I can not find a source that would explicitly state picolinamide undergoes Hofmann rearrangement to form 2-aminopyridine. Does this reaction occur, and if not, why?
user avatar
  • 1
5 votes
1 answer
128 views

Does the Oxy or Alkoxy Claisen Rearrangement Exist?

@Waylander's cogent Comment to the query of @Random Guy inspired me to post a problem in synthesis to test a question I have pondered for some time. The activation energy (AE) for the Cope ...
user avatar
  • 13.3k
1 vote
0 answers
85 views

Why doesn't the protonated propyne rearrange? [closed]

In the reaction of propyne with $\ce{HBr}$ this cation (prop-1-en-2-ylium) was mentioned by my teacher: $$\ce{H3C-\overset{+}{C}=CH2}$$ He told me that the carbocation will not rearrange as it will ...
user avatar
  • 191
7 votes
3 answers
445 views

What is abnormal Beckmann rearrangement?

What is abnormal Beckmann rearrangement? I read this term in one of my solution papers but I am not able to find relevant literature for the same. Answers linking to some source, or giving the ...
user avatar
  • 1,329
9 votes
1 answer
129 views

Weerman degradation on alpha-hydroxy amides

I came across this reaction scheme in the solutions of a test paper: I understand the formation of isocyanate intermediate as the first step. In the second step, I realized that hydrolysis will be ...
user avatar
  • 1,773
2 votes
0 answers
56 views

Migratory aptitude of chlorobenzene vs nitrobenzene in pinacol-pinacolone

I do know the basic order of migratory aptitude in pinacol-pinacolone rearrangement, which is usually said as subject to reaction conditions. However, I wanted to know how can I compare the migratory ...
user avatar
  • 1,329
-4 votes
1 answer
54 views

Does rearrangement occur in schmidt reaction? [closed]

I recently read about schmidt reaction in which a carboxylic acid is converted to an amine. While forming this, acyl carbocation $(\ce{RCO+})$ is formed, so does rearrangement takes place or reaction ...
user avatar
0 votes
0 answers
57 views

Why is there a phenyl shift in this reaction?

Why is there a phenyl shift in this reaction. I believe that the +R effect by 2 phenyl groups would be better than the +R effect by oxygen because of its lone pair. Can somebody please confirm?
user avatar
  • 141
4 votes
2 answers
334 views

Why and how does ring expansion occur in the dehydration of (cyclobut-3-ene-1,2-diyl)dimethanol?

Can someone explain how does this ring expansion occur with the mechanism? I do understand that the hydride shift occurred because of carbocation stability but why did the ring expand? Can you please ...
user avatar
  • 141
5 votes
0 answers
56 views

Why does this carbocation undergo further rearrangement? [duplicate]

I am trying to figure out the product of this reaction. I initially thought that a carbocation would be formed at where the chlorine leaves from: But according to the answer stated by the textbook,...
user avatar
7 votes
1 answer
120 views

Does a reaction proceed through SN1 if rearrangement results in a stable carbocation?

While going through my book I came across the following problem: I thought it was safe to assume that the secondary alcohol would give SN1(although secondary alcohols give significant amount of both ...
user avatar
5 votes
3 answers
256 views

Possible carbocation rearrangement in substitution reaction to give two different products

In the following substitution reaction, is compound I formed by $\mathrm{S_N}$2 and compound II formed by $\mathrm{S_N}$1 and carbocation rearrangement? Or is there some rearrangement I'm not aware ...
user avatar
  • 119
4 votes
0 answers
99 views

Beckmann Rearrangement in cyclic compounds

Consider 1-indanone: I am supposed to find the rearrangement product on treating this with hydroxylamine (which gives an oxime) and then $\ce{H+}$ (with heat). I am aware of the mechanism of Beckmann ...
user avatar
2 votes
0 answers
55 views

Products of the reaction between cyclohexanone and N-bromosuccinimide

Problem Treating cyclohexanone with N-bromosuccinimide in the presence of carbon tetrachloride gives A. A on treatment with aqueous KOH gives B. Deduce the structures of A and B. Solution Questions ...
user avatar
1 vote
1 answer
54 views

How does temperature and other factors affect sigmatropic rearrangements?

The image below shows a [3,3] sigmatropic rearrangement. My question is why does the increased temperature favour the right side? The arrangement is technically the same except for the methyl groups ...
user avatar
  • 1,160
2 votes
0 answers
57 views

Show the mechanism of the Pinacol-Pinacolone Rearrangement reaction [duplicate]

In the reactant, due to $\ce{H+}$ ion, a positive charge will be created by removing water in place of the rightmost $-\ce{OH}$. But then how will it give such a product. I cant see any way to make ...
user avatar
0 votes
1 answer
57 views

Carbocation rearrangement

I am dealing with some basic reactions in organic chemistry. One of these is the acid reflux of alcohols. Something I came across was hydride shifts. I know how and why they occur, but I don't ...
user avatar
1 vote
0 answers
76 views

Hydrogen isotope effect on methyl shift

Consider this typical 1,2 methanide shift in a carbocation: Which isotopic form of methanide ($\ce{CH3, CD3, or CT3}$) would migrate from secondary carbocation to form more stable tertiary ...
user avatar
  • 1,119
0 votes
1 answer
141 views

Baeyer-Villiger Oxidation restricted to Ketones

According to Wikipedia, Baeyer Villiger oxidation occurs at the electron deficient oxygen site, with elimination of the carboxylate ion, and migration of an R group. But it is restricted to ketones ...
user avatar
13 votes
1 answer
202 views

Mechanism for the addition of hydrogen iodide to 3,3‐dimethylbut‐1‐yne

The following reaction mechanism was given as a solution to a solved problem in my textbook1 for the addition of hydrogen iodide to 3,3‐dimethylbut‐1‐yne: It can be seen that that 2,2-diiodo-3,3-...
user avatar
  • 1,952
0 votes
0 answers
148 views

Extent of multiple hydride shifts in a carbocation

Take this example: Multiple hydride shifts are possible only if in each step, the formed intermediate is more stable than the previous one. (1) to (2) converts $2^\circ$ carbocation to $3^\circ$ ...
user avatar
  • 1,119
1 vote
1 answer
222 views

Acid catalysed dehydration of alcohol with a bicyclo group

Pathway 1: Rate determining step is the formation of carbocation. In this pathway, a conjugated tertiary carbocation is generated as an intermediate. Pathway 2: One of the resonance form of ...
user avatar
  • 1,119
0 votes
1 answer
86 views

Acid catalysed dehydration of 5-methylidenecyclopent-2-en-1-ol [closed]

I think the following reaction is NOT possible. I could not find a mechanism for ring expansion. Is ring expansion possible in any way? Is the following mechanism correct?
user avatar
  • 1,119
1 vote
2 answers
90 views

Dehydration of primary alcohol with a cyclobutadiene substituent [closed]

Note: Primary alcohol will follow E2 mechanism, therefore, removal of protonated water and proton (RDS) shall proceed in a single step in the above mechanism. My questions are: 1- According to ...
user avatar
  • 1,119
3 votes
1 answer
1k views

Beckmann rearrangement v/s dehydration of Oximes

In the above question, A is an oxime, which is then reacted with phosphorus pentoxide. Now, phosphorus pentoxide is both a dehydrating reagent and a reagent used for Beckmenn rearrangement, but which ...
user avatar
0 votes
1 answer
66 views

Ring expansion in cyclo compounds

In the following reaction, why does ring expansion not take place? Mechanism that was the correct one: In the second step when there is a protonated carbon the ring should expand to become 6 ...
user avatar
0 votes
1 answer
276 views

Preparation of Grignard reagent. Free radical rearrangement

Mechanism of formation of Grignard Reagent $$\ce{R-X + ^.Mg^. ->[\text{r.d.s.}] R^. + ^.Mg+X-} $$ $$\ce{R^. + ^.Mg+X- -> R-Mg+X-} $$ As the mechanism of preparation of Grignard reagent suggests,...
user avatar
1 vote
0 answers
97 views

What the product of this reaction?

The reaction is as follows, with (i) being my answer, and (ii) being the correct answer in the book. My question is why is the product (ii) formed here and elimination not favoured here? I think that ...
user avatar
7 votes
1 answer
468 views

Hydrolysis of (chloromethyl)cyclopropane: Is but-3-en-1-ol a possible product?

This is from one of the practice papers for the JEE , asks for possible hydrolysis products of (chloromethyl)cyclopropane . Product A happens to be due to stability of cyclopropyl methyl carbocation. ...
user avatar
1 vote
0 answers
167 views

Predict the products of the following reactions with Mechanism [closed]

1 My Attempt : The correct answer is C. I tried rearranging similar to claisen rearrangement but I have no clue how to go forward. I know that option A is wrong and that the product is pretty easily ...
user avatar
2 votes
1 answer
185 views

Why does ring contraction take place in Wagner–Meerwein rearrangement?

An example of Wagner–Meerwein rearrangement given in my textbook is substitution by $\ce{AgNO2}$ in iodocyclohexane. One of the product, cyclopentylnitromethane is through ring contraction. I don't ...
user avatar
  • 423
-1 votes
1 answer
50 views

Rearrangement of 1,1-Dichloro-1a,9b-dihydro-1H-cyclopropa[l]phenanthrene on heating

Due to angle strain , the three membered ring is not stable. So i think it would break and kick out one of the chlorine atoms resulting in the formation of a carbene. But i don't know how to proceed ...
user avatar
4 votes
1 answer
109 views

Is the Beckmann Rearrangement technically an "SN2" reaction at an "sp2" center?

Below is the mechanism from this link of the Beckmann Rearrangement. In the alkyl migration step, the alkyl group migrates simultaneously as the $\ce{H2O}$ leaving group is expelled. This seems as ...
user avatar
  • 1,929
9 votes
2 answers
421 views

Photochemical rearrangement of 4,4‐diphenylcyclohexa‐2,5‐dien‐1‐one

I can see how the option A and B are correct as it is just a standard dienone–phenol type reaction which involves a phenyl shift. However, the given answer is A, B, C and D. I do not see how C and D ...
user avatar
7 votes
1 answer
201 views

Does the nitrogen atom move with in the molecule in an ammonia maser, or does the molecule flip?

This intriguing answer to Can reactions produce microwave or radio wave radiation? says (in part): An ammonia maser qualifies as an inorganic RF-emitting reaction. As the nitrogen changes position in ...
user avatar
  • 6,112
0 votes
0 answers
69 views

Which of the following compound will undergo rearangement?

Question Attempt I believe the answer should be B,C and D. In C and D the oxyge(or Nitrogen in D) can rearange by donating lone pair to carbocation. But the books answer says B. Where am I wrong. ...
user avatar
7 votes
1 answer
441 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 ...
user avatar
2 votes
2 answers
262 views

Anti-Markovnikov addition of HCl

The following reaction has been troubling me for a while now. Since peroxides won't give the anti-Markovnikov product when used with HCl, I cannot think of any reagents that would result in the ...
user avatar
-1 votes
1 answer
121 views

Unable to form the product formed via rearrangement

Ok so I first reacted one of the carbonyl groups with NH2OH to form an oxime. And then a Beckmann rearrangement takes place followed by tautomerism. Then the lone pair on nitrogen did an ...
user avatar
5 votes
1 answer
472 views

Acid-catalysed isomerisation of phenyl epoxide to aldehyde

How does $\ce{H3O+}$ cause the formation of an aldehyde from the following epoxide? I thought that the epoxide would undergo opening to form a 1,2-diol, as illustrated below. Am I wrong?
user avatar
1 vote
1 answer
261 views

Intramolecular Reaction with carbocation rearrangement

I came across a question recently which is as follows, I came up with a mechanism but I am stuck at a step as I am unable to reason out the driving force. Step(3) has a hydride shift and its next ...
user avatar
  • 1,194
1 vote
1 answer
654 views

Question on ring expansion

In the orange box, I think that the blue-carbon should be a carbocation instead. So, option A should be correct. But, the answer is B. Why is it so?
user avatar
  • 2,767
8 votes
3 answers
2k views

Reaction mechanism of rearrangement

I am currently studying for my organic chemistry exam, but there is one problem I do not understand. Unfortunately, I do not have any solutions. See image for the problem. My first thought was the ...
user avatar
3 votes
1 answer
146 views

Rearrangement considerations in feasibility of SN1 in given reactants

I have been asked to compare the feasibility of Unimolecular Nucleophilic Substitution ($\mathrm{S_N1}$) in the following question. I have received instruction that the reaction will be feasible only ...
user avatar
6 votes
2 answers
2k views

Tiffeneau–Demjanov rearrangement products

With reference to the paper McCasland, G. E. Pinacolic Rearrangements of Epimeric Aminocyclanols. J. Am. Chem. Soc. 1951, 73 (5), 2293–2295 DOI: 10.1021/ja01149a110. (ResearchGate link). It states ...
user avatar
5 votes
4 answers
280 views

8a-methyl-1,2,3,4,4a,8a-hexahydronaphthalen-4a-ylium carbocation rearrangement

In this reaction after the attack of lone pairs on $\ce{H+}$ ions, a stable $3^{°}$ carbocation is formed. But seeing the six membered ring and the double bonds already present, I can't help but think ...
user avatar