Questions tagged [rearrangements]

For questions about specific rearrangements within organic chemistry.

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4
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1answer
37 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 ...
-1
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0answers
19 views

How many types and to what extent are shifts possible in rearrangements in organic molecules? [closed]

I searched on the internet but couldn't find everything at a single place with complete explanation
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0answers
52 views

Predicting the products for free radical rearrangement reaction [duplicate]

We were taught about rearrangement reaction and were given this homework: My attempt I cleaved the carbonyl bond homogeneously and proceeded to get product A; But I can't figure out the others; A ...
9
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2answers
209 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 ...
6
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1answer
112 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 ...
0
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0answers
25 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. ...
7
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1answer
154 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 ...
2
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2answers
116 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 ...
-1
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1answer
104 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 ...
5
votes
1answer
142 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?
1
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1answer
79 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 ...
1
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1answer
149 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?
7
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3answers
463 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 ...
2
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1answer
86 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 ...
5
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2answers
565 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 ...
4
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4answers
234 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 ...
4
votes
1answer
326 views

Mechanism of Fritsch–Buttenberg–Wiechell rearrangement

The following reaction was given, which uses potassium t-butoxide. The solution to this problem was given as follows: Step 1 is the attack of strong base, t-butoxide, on the vinyl proton. Step 2 ...
1
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0answers
186 views

Retention of configuration in Hofmann rearrangement

Why is there a retention of configuration in Hofmann bromamide degradation/Hofmann rearrangement? I would think that there should be an inversion of configuration due to the migration of alkyl group ...
2
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2answers
329 views

Rearrangment during alkyne synthesis

What I have got as (G) is this. $\hskip1in$ My questions How the rearrangement from (G) to $non-1-yne$ can happen i.e. its mechanism? Why Sodium Amide in particular yield terminal alkyne, unlike ...
1
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0answers
83 views

Ring contraction in benzilic rearrangement

Wikipedia says that, Benzilic acid rearrangement occurs with ring contraction when used on cyclic diketones. But gave no explanation, can you please elaborate on this with some mechanism. One ...
2
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1answer
48 views

Determining ratio of competing fragmentation processes in mass spectrometry

In a photoionization experiment, three photons of wavelength 266 nm were absorbed by a neutral molecule of 6-methyl-2-heptanone. If the kinetic energy of the electron removed during ionization is 1.4 ...
4
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1answer
245 views

The oxidation of aldehydes and alpha-diketones with peroxy compounds

Recently, I have been reading up on the Baeyer-Villiger (BV) oxidation. The oxidation is most commonly discussed for ketones. However, the oxidation also works for aldehydes and $\alpha$-diketones (...
0
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1answer
125 views

Benzilic acid rearrangement

I'm in need for the exact mechanism of the above reaction. I attempted some tries(mentioned in the mechanism above) and I felt the yield quite unsatisfactory. - the last step remains stuck in an ...
5
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0answers
175 views

Shouldn't the 5-membered ring expand to a six membered one in this nucleophilic addition reaction?

I am dealing with a problem involving addition of $\ce{HCl}$ to a ring: According to what I think, the ring should expand to a six-membered following carbocation formation at the tertiary site, as a ...
0
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1answer
247 views

Reaction mechanism for the conversion of acyl hydrazide to acyl azide

How is an an acyl hydrazide converted into an acyl azide in the presence of $\ce{HNO2}$? According to me, the $\ce{-NH2}$ group of hydrazide will get converted into $\ce{-N2+}$ through $\ce{HNO2}$. ...
9
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1answer
540 views

Ring contraction when cyclohexene oxide is treated with methyl Grignard

My book writes that: Recall that epoxides rearrange with Lewis acids in a pinacol-like fashion, and that Grignard reagents in THF exist in the following equilibrium: I approached this ...
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0answers
73 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 ...
3
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0answers
192 views

Major product of isomerization reaction

I am trying to come up with a logical mechanism for the following transformation, where 2-methylenecyclobutan-1-ol is converted to cyclopentanone under acidic conditions: What I have tried to do was ...
4
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0answers
311 views

Regioselectivity of the Beckmann rearrangement

It seems to be that the Beckmann rearrangement is a nice way to prepare secondary amines. This can be achieved by removal of oxygen via the use of $\ce{HI}$/$\ce{P}$. However, if ketones are used, ...