Questions tagged [c-c-addition]
For questions about addition to C–C π bonds (i.e. C=C or C≡C).
40
questions
4
votes
1answer
85 views
Can someone explain my professor's answers for these alkene additions? [closed]
(a) Why would cyclohexane expand into cycloheptane? Cyclohexane is stable.
(b) Why would cyclopentane not ring expand into cyclohexane? In the process a tertiary carbocation would be formed just like ...
2
votes
0answers
31 views
Varying sizes in LUMO of acrolein
I want to ask a question about the varying sizes in the LUMO of acrolein during a 1,2- or 1,4-addition.
Today in our introductory lesson to Organic Synthesis with 1,2- and 1,4-addition we were ...
1
vote
0answers
57 views
If alkyl-substituted alkenes are more stable, how does one explain their increased addition reactivity?
My understanding is that in alkyl-substituted alkenes there is hyperconjugation between $𝜎(\ce{C−X})$ and $𝜋^∗(\ce{C=C})$. I also have read that more alkyl-substituted alkenes are many folds more ...
0
votes
0answers
219 views
What is the major product of the reaction of 2-methyl-but-1,3-diene with HBr?
What is the product of the reaction of 2-methyl-but-1,3-diene with HBr?
What I understand is that carbon (2) will get a positive charge after protonation.
But after this, which should be the major ...
0
votes
0answers
33 views
Addition v/s elimination with double bond and OH together
If a compound has both an hydroxyl group and a double bond and we add $\ce{HBr}$ to it,
(a) substitution reaction to the hydroxyl group can take place, or
(b) an addition reaction of a ...
5
votes
0answers
143 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
votes
2answers
163 views
Markovnikov Rule of Alkenes
$$\ce{CH3CH(CH3)CHCHCH2CH3 + HBr ->}$$
According to Markovnikov Rule, "the rich get richer". But, as we can see the 2 carbons have the same amount of $\ce{H}$. So, what's probably the answer?
0
votes
0answers
594 views
Electrophilic addition of IBr to alkene
I would assume options A and B are possible products due to the $\ce{I+}$ electrophile attacking the alkene, and hence are ruled out.
However, I am torn between options C and D. Both products are ...
5
votes
1answer
276 views
Regioselectivity of bromination of alkenes
Recently, in my chemistry lesson, we were discussing the mechanism of the bromination of alkenes. The teacher brought up the involvement of the cyclic bromonium intermediate. She also mentioned that ...
3
votes
0answers
117 views
Mechanism of photochemical hydroamination with LDA
I've recently come across a couple examples of intramolecular alkene hydroamination accomplished by treatment with LDA followed by visible light irradiation (tungsten light bulb):[1,2]
I'd assume ...
0
votes
1answer
60 views
How far-reaching is the effect of conjugation?
Due to conjugation, it is possible for 1,4-addition, or conjugate addition, to occur. I was thinking, since conjugation and resonance effects do no diminish with distance, unlike inductive effects, ...
3
votes
1answer
97 views
Conjugate addition vs Electrophilic addition
I was just doing an organic chemistry problem from an online source recently, on the topic of conjugate additions (or 1,4-additions). Below is an image illustrating the problem.
I chose the upper ...
2
votes
1answer
239 views
On the addition of HCl to a conjugated diene [closed]
Is this allylic chloride formed by an ionic or radical mechanism? Is it the more stable isomer?
3
votes
0answers
157 views
Sigma bond behaving as stronger nucleophile despite presence of pi bond?
In my book, the following reaction is given
The solution states that the sigma bond between hydrogen and carbon (3 degree) in isobutane attacks $\ce{H+}$ from $\ce{HF}$ to generate tert-butyl ...
1
vote
1answer
552 views
Why do more substituted alkenes undergo epoxidation, but the less substituted alkenes undergo hydrogenation?
We know that, in case of a choice, catalytic hydrogenation will hydrogenate the less substituted alkene, because the less substituted alkene is less stable. But, we also know that, in case of a ...
5
votes
1answer
734 views
Why doesn't the bromide anion attack during electrophilic addition of bromine in methanol solvent?
It is known that addition of bromine (in methanol) to ethene will yield 1-bromo-2-methoxyethane. The reaction proceeds with the formation of a bromonium intermediate in the first step. In the second ...
7
votes
1answer
237 views
How to decide what pathway a reaction will follow, elimination, addition to a carbonyl or nucleophilic substitution?
There is a substrate such as this,
and it is treated with alcoholic KOH.
I know that a hydrogen in $\alpha$-position to the carbonyl group will be abstracted, leaving a carbanion. My query lies in ...
0
votes
1answer
155 views
In halogenation of ethene using bromine for example, why does the lone pair of bromine attack the C atom?
In the presence of the electron rich (pi bond) of ethene, the bromine molecule becomes a temporary induced dipole, one end being electron deficient and acting as the electrophile. (The pi bond in) ...
3
votes
1answer
411 views
In the presence of an electron-rich species, why is Br2 the stronger electrophile than water? [closed]
In the electrophilic addition of aqueous bromine to ethene, the first slow step involves the electron rich (pi bond) of ethene attacking the bromine molecule to form a carbocation and Br-:
And, then ...
8
votes
2answers
1k views
Bromonium ion or Mesomeric effect ( intermediate during addition to alkenes)
It's mentioned in Peter Sykes , A Guidebook To Mechanism In Organic Chemistry , 6th edition, 13th impression by Pearson, Pg. No. 185 , that on addition of $\ce{HBr}$ to bromoethene the only product ...
2
votes
1answer
179 views
Electrophilic addition to alkenes
Consider the addition of HBr (in absence of any radical initiators or environment that promotes radical mechanistic pathway), to 3-bromocyclopentene.
The first step is the attack of $\ce{H^+}$
On the ...
6
votes
1answer
327 views
Why must polymers have a repeating unit?
In organic chemistry, we learned that small molecules can form a polymer via a process called polymerization. For example, $\ce{CH2=CH-Br}$ molecules can form the polymer
\begin{align}
\ce{nCH2=CH-Br-...
5
votes
1answer
177 views
Intramolecular lactonisation in an unsaturated carboxylic acid
I am having some trouble figuring out how this reaction proceeds:
Attempt 1: The most obvious thing to do is deprotonate the acid group. I tried using the carboxylate group to attack the alkene, ...
0
votes
1answer
740 views
Regioselectivity in addition of hydrogen iodide to vinyl chloride
I encountered a question which was stated as:
The reaction of vinyl chloride with hydrogen iodide to give 1-chloro-1-iodoethane is an example of anti-Markovnikov addition. Is this true or false?
...
8
votes
1answer
816 views
Why does boron add to the less substituted carbon in the hydroboration of an alkene?
In the hydroboration of a typical alkene, the boron fragment ends up attached to the less substituted carbon:
What are the electronic or steric factors that lead to this regioselectivity?
0
votes
2answers
4k views
Reactivity order in hydrogenation reaction of but-2-yne and butene isomers
Question 1:
The reactivity order towards hydrogenation of the following compounds is:
but-2-yne ($\ce{CH3-C\bond{3}C-CH3}$)
cis-but-2-ene ($\ce{CH3-CH=CH-CH3}$)
trans-but-2-ene ($\ce{...
3
votes
2answers
410 views
Product of the addition of 1 eq. bromine to 1-methylcyclohexa-1,4-diene
When we add one equivalent of $\ce{Br2}$ then which double bond will get brominated?
The double bond in the molecule with methyl group will be more stable as it will have more hyper conjugating ...
15
votes
3answers
4k views
Why does bromine add to a double bond instead of a triple bond if both are present?
According to my textbook, the addition of bromine to pent-1-en-4-yne at low temperature yields 4,5-dibromopent-1-yne:
Why does bromination of the double bond occur selectively?
2
votes
1answer
1k views
What is the stereochemistry resulting from hydroboration of 1-methylcyclopentene?
What is the major product of the following reaction sequence?
I'm supposed to work out the structures of both 2 and 3, but I already know 2 to be 1-methylcyclopentene (as the most substituted ...
7
votes
1answer
989 views
Why does the chlorination of indene occur with syn selectivity in heptane?
In the chlorination of indene to form 1,2-dichloro-2,3-dihydro-1H-indene in heptane as solvent, the syn dichloride is formed as the major product, as reported in J. Org. Chem. 1980, 45 (25), 5150–...
10
votes
2answers
1k views
Getting 3,4-dimethylhex-3-ene from but-2-ene
How can one get 3,4-dimethylhex-3-ene from but-2-ene ?
$\hskip2in$
Using $\ce{Br_2}$ then two equivalents of $\ce{CH_3CH_2MgBr}$, I can get the corresponding alkane (3,4-dimethylhexane) but I don't ...
5
votes
1answer
669 views
Addition reaction of hydroiodic acid to 2-bromo-3-chloro-2-butene
How can the major product of the addition reaction of 2-bromo-3-chloro-2-butene with hydroiodic acid be predicted, since Markovnikov's rule fails to distinguish it?
$$\ce{H3C-C(Cl)=C(Br)-CH3~+~HI~-&...
10
votes
2answers
6k views
What are the products of the reaction of 1-methoxycyclohexene with dilute hydrochloric acid?
When 1-methoxycyclohexene is treated with dilute aqueous hydrochloric acid, methanol is produced along with another organic product. Identify this product. Explain why methoxycyclohexane is inert ...
7
votes
1answer
3k views
What is the difference between “bromine” and “bromine water” in their reaction with an alkene?
In question 16 of the A-Level Chemistry 2013 exam, there is this reaction scheme:
$$\ce{CH3CH=CH2 ->[?] CH3-CHBr-CH2Br}$$
The question asks for both the name of the reagent and the product. I ...
7
votes
2answers
1k views
Hydroboration/oxidation vs acid-catalyzed hydration of 1-phenylpropene
I am trying to predict the products of both the hydroboration/oxidation and acid-catalyzed hydration of 1-phenylpropene:
Both C1 and C2 of the double bond are secondary carbons. However, I have the ...
1
vote
1answer
1k views
What is Markovnikov's rule?
What is Markovnikov's rule? How can we use it to predict the products of additions to alkenes? And is it always obeyed, or are there exceptions to this rule?
9
votes
1answer
7k views
Order of reactivity of carbonyl compounds to Nucleophilic addition reaction
One of the questions in my textbook was to arrange the following in order of their reactivity for nucleophilic addition reaction.
$\ce{(p-NO2Ph)_2CO}$
$\ce{(CH3)_2CO}$
$\ce{(p-NO2Ph)COH}$
$\...
3
votes
1answer
782 views
Regioselectivity in Kharasch addition of bromotrichloromethane
When hex-1-ene is treated with bromotrichloromethane in the presence of a peroxide initiator (e.g. dibenzoyl peroxide), what is the regioselectivity of the addition?
I know that the radical addition ...
2
votes
1answer
205 views
Products for the hydrogenation of the cycloalkene in (3R,4R,5S)-4,5-diamino-3-(pentan-3-yloxy)cyclohex-1-ene-1-carboxylic acid
Write the products (more than one) for the hydrogenation of the cycloalkene ring in (3R,4R,5S)-4,5-diamino-3-(pentan-3-yloxy)cyclohex-1-ene-1-carboxylic acid. Reagents are molecular hydrogen with ...
11
votes
1answer
2k views
Resonance in carbocation derived from allenes
During a reaction if addition on one of the $\pi$ bonds of an allene (containing even number of $\pi$ bonds like $\ce {H2C=C=CH2}$) takes place then a carbocation is formed. To decide the position of ...
