Questions tagged [c-c-addition]

For questions about addition to C–C π bonds (i.e. C=C or C≡C).

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4
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1answer
58 views

Can someone explain my professor's answers for these alkene additions? [on hold]

(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
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0answers
23 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 ...
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0answers
41 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 ...
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119 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 ...
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32 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
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0answers
129 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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2answers
136 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?
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425 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
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1answer
224 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
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0answers
109 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
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1answer
55 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
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1answer
88 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 ...
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1answer
213 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?
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123 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
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1answer
472 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
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1answer
637 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
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1answer
216 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
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1answer
137 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
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1answer
360 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 ...
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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
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1answer
166 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
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1answer
296 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
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1answer
170 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
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1answer
689 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
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1answer
747 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?
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2answers
3k 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
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2answers
382 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
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3answers
3k 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
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1answer
842 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
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1answer
964 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-1​H-indene in heptane as solvent, the syn dichloride is formed as the major product, as reported in J. Org. Chem. 1980, 45 (25), 5150–...
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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
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1answer
656 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
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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
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1answer
2k 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
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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 ...
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1answer
951 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
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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
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1answer
729 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
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1answer
201 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
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1answer
1k 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 ...