14
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Why does boron add to the less substituted carbon in the hydroboration of an alkene?
For the hydroboration of isobutene
there is a steric aspect:
And though sterics may play some part, it doesn't explain near 100% regioselectivity. More important in determining regiochemistry, I ...
- 24.1k
11
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Regioselectivity of bromination of alkenes
With bromination, the first step is the formation of an adduct complex, which can be explained that the π-bond polarises the dibromide. The next step is the formation of the bromonium ion, which ...
- 44.3k
10
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Intramolecular lactonisation in an unsaturated carboxylic acid
The reaction as you are given turns up no results in SciFinder, meaning it has not been reported in any scientific journal. It is thus the imagination of whoever set the test.
However, closely ...
- 68.5k
8
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Does rearrangement take place in the reaction between ethenylcyclohexane and iodine chloride?
Yes, I believe the rearrangement can happen. However, the product from the rearrangement is probably not the major one.
The closest reaction to what you have drawn that I could find on SciFinder is ...
- 5,715
8
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Product of oxymercuration-demercuration reaction
Well, the answer is correct except instead of -OH it must be -OMe because the reagent used is Hg(OAc)2/ MeOH and not Hg(OAc)2/H2O.
Here's an illustration of the rection using methanol
- 96
8
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What type of interaction in a π-complex?
Different communities differ in how to represent complexes, for instance with $\pi$ nucleophiles as Lewis base, and electron density between atoms (see an earlier thread here). To count for each line ...
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7
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Reaction of alkane with alkene in acidic medium
This reaction is actually called as
"alkylation of alkenes". If I had known this term, I could have directly searched it on internet but won't have asked it on SE ;)
https://chem.libretexts....
- 340
6
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Stereoselectivity of ring closure in intramolecular iodolactonisation
The results of the iodolactonization example presented in this question were published in 1982 by Bartlett, et al.1 While @Aniruddha Deb has captured the essence of the reaction, there is more than ...
- 17.3k
5
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Why doesn't the bromide anion attack during electrophilic addition of bromine in methanol solvent?
There's a very simple explanation for this. Your reasoning regarding $\ce{Br-}$ being a better nucleophile is absolutely correct. The reason as to why methanol attacks instead of $\ce{Br-}$ is because ...
- 5,532
5
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Method for regioselective hydroalkylation of terminal alkyne
Here is a potential solution using old-school chemistry, though with several steps.
Hydroborate the alkyne and work up with $\ce{H2O2}$ to give the aldehyde.
Alkylate the aldehyde enolate with $\ce{...
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5
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Anti-Markovnikov addition of HCl
One way to do it would be do first do a hydroboration-oxidation reaction, which leads to the anti-Markovnikov addition of $\ce{H2O}$. So you will get an $\ce{-OH}$ group instead of $\ce{-Cl}$. Then, ...
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How can a β,γ-unsaturated ketone be converted to 1-pyrroline?
I suggest two possible approaches. Narasaka, et al. have effected similar cyclizations photochemically. I prefer to start with the allylic alcohol 1 to avoid complications with oxime formation. ...
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5
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Electrophillic susbtitution of bromine on styrene and cinnamic acid in the presence of FeBr3, a Lewis acid
In electrophilic aromatic substitution the activation energy is very high ( as it should be, since the aryl carbocation transition state is very unstable)
The role of $\ce{FeBr_3}$ or any lewis acid ...
- 1,524
5
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What is the meaning of a “halide component” for Friedel–Crafts reaction?
Friedel–Crafts reactions proceed through the alkylation or acylation of an aromatic ring using an alkyl halide. Considering the alkyl halide compound of the form
$$\ce{R-X}$$
where $\ce{R}$ is the ...
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4
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Stereoselectivity of ring closure in intramolecular iodolactonisation
Without further details, I would say that both products are possible.
The reaction that you have given here is an Iodolactonization reaction. You have correctly identified that the tert-butyl group ...
- 6,278
4
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What are the products of alkene oxymercuration with diols?
There are so many structures here that it is at times difficult to keep things straight. The best way to approach your question is to take advantage of what is known about oxymercuration. If you enter ...
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4
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Bromonium ion or Mesomeric effect ( intermediate during addition to alkenes)
You are not going to see the formation of a primary carbocation—the activation energy is too high. Even though it is true the following are resonance structures of one another:
the geometry in which ...
- 24.1k
4
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Why must polymers have a repeating unit?
Entropy would favour a random orientation of each monomer unit when building up the chain, however whenever you have two different substituents at the ethylene unit, then electrostatics and sterical ...
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4
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Conjugate addition vs Electrophilic addition
Grignards unless modified with Cu(I) salts add 1,2 not 1,4 so the EtMgBr will add to the ketone to give the t-alcohol and leaving the double bond intact.
Consider then the HCl step - if it is strong ...
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4
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Why do more substituted alkenes undergo epoxidation, but the less substituted alkenes undergo hydrogenation?
As you already know, the alkene has to approach the catalyst surface in the first step. For optimum adsorption, the molecule must be able to orient itself parallel to the surface of the metal. Less ...
- 5,532
4
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Product of the addition of 1 eq. bromine to 1-methylcyclohexa-1,4-diene
You misunderstood what hyperconjugation is. It occurs when the electrons in a $\ce{C-H}$ $\sigma$-bond are shared with an adjacent atom's empty or partially filled $\mathrm{p}$-orbital, giving the ...
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4
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What are the major products when naphthalene reacts with ethyl chloride in the presence of AlCl₃?
TL;DR: The final product will depend on what solvent you are using, what temperature the reaction is being operated and the concentration of the reactants.
Long answer
From the abstract of this paper1:...
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Why does bromine add to a double bond instead of a triple bond if both are present?
I'm going to take "more reactive" as in the alkene undergoes bromination at a faster rate than the alkyne, which seems to imply that the activation energy of the transition state is greater.
A ...
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votes
Does rearrangement take place in the reaction between ethenylcyclohexane and iodine chloride?
In Bull. Chem. Soc. Jpn. 1983, 56 (1), 314–317, a paper dealing with the kinetics of addition of $\ce{ICl}$ to alkenes, the following mechanism is proposed
This may lead to the conclusion that the ...
- 7,050
3
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The dependency on electron density in the reactivity order of electrophilic and nucleophilic additions
After not having any answer for over a week, I wrote about this question in the comments of an answer I had posted to another question. There another user confirmed that the reasoning I have given in ...
- 1,817
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Major product formed when HBr is added to 1-phenyl but-2-ene
Phenyl groups are bulky and cause steric hindrance.
This makes the $\ce{Br^-}$ nucleophile have an easier time targeting the carbon atom in the double bond that's closer from the right side of the ...
- 1,812
2
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Hydroboration/oxidation vs acid-catalyzed hydration of 1-phenylpropene
Hydroboration
With the simplest hydroborating agent $\ce{BH3.THF}$, the hydroboration/oxidation of 1-phenylpropene proceeds to give 1-phenylpropan-1-ol as the major product.[1] The isomer of the ...
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2
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Ozonolysis of alkene
When the ozonide is reduced to Ketone/Aldehyde, We're concerned with what is called the "reductive workup" . We can summarize it like this:
If we look a little further into the mechanism (...
- 426
2
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Can someone explain my professor's answers for these alkene additions?
In example A, you are right that the cyclohexane ring is more stable than the cycloheptane ring. There are two choices for rearrangement in this case:
1) Ring expansion to form the cycloheptane ring ...
- 2,010
2
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Markovnikov Rule of Alkenes
My suggestion is to stop trying to predict the product by rules like “rich becomes richer” or “proton goes to carbon having greater number of hydrogens attached to it”, etc. for Markovnikov addition ...
- 1,047
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