Solving Alkene Reactions Problems for Chem Exam

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Discussion Overview

The discussion revolves around solving problems related to alkene reactions in preparation for a chemistry exam. The focus includes mechanisms of addition reactions, particularly with bromine and methanol, as well as the behavior of conjugated and isolated dienes.

Discussion Character

  • Homework-related
  • Exploratory
  • Technical explanation

Main Points Raised

  • One participant questions whether 1,3-cyclohexadiene should be treated as a conjugated diene, suggesting that bromine could add in both 1,2 and 1,4 positions, leading to two products.
  • Another participant asks if 1,4-cyclohexadiene should be considered an isolated diene and where bromine would add, also inquiring about the possibility of two products from different double bonds.
  • There is a query about the mechanism for the formation of two products when propylene is treated with bromine in methanol, noting that while one product is straightforward, the second product's formation is unclear, especially regarding the role of methanol.
  • A participant suggests that the reaction of 1,2-dimethylcyclopentene with BH3 and H2O2/NaOH would yield the same product as direct hydrolysis due to the symmetry of the alkene.
  • Responses indicate that the addition reactions may be condition-dependent, and one participant encourages drawing mechanisms to clarify the addition process.
  • There is a mention of the importance of understanding the intermediate in halogenation reactions.
  • A later reply references a previous discussion about the locant for the alkene, suggesting uncertainty about the hydrolysis outcome.

Areas of Agreement / Disagreement

Participants express uncertainty and explore multiple viewpoints regarding the addition mechanisms and products formed in the reactions discussed. No consensus is reached on the specific outcomes or mechanisms.

Contextual Notes

Some claims depend on specific reaction conditions and assumptions about the structures involved. The discussion includes unresolved questions about the mechanisms and products of the reactions.

Who May Find This Useful

Students preparing for chemistry exams, particularly those focusing on organic chemistry and reaction mechanisms involving alkenes and dienes.

ChemDoodle
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Hey I'm studying for my chem exam & I am having difficulty solving some problems.

1. 1,3cyclohexadiene + Br2= ?
Here,should i treat it like a conjugated diene? Meaning that the Br molecules will have 1,2 and 1,4 additions on the diene and 2 products will be there?

2. 1,4cyclohexadiene + Br2 = ?
Here should i t eat it like an isolated diene? & if so..where should the Br add? On which bond? Or will there be 2 products? With Br adding on the 1 double bond in the first & 4 double bond in the second?

3. When propylene is treated with bromine in methanol (CH3OH),two products are formed C3H6Br2 & C4H9BrO.Explain meachanistically how each are formed.
Here,the first product is simple..its obtained by halogenation of alkenes..simple addition of the Br molecules on the pi-bond.But i wasn't able to determine how the second product is obtained? Obviously methanol has something to do with it..But what kind of reaction is it? We studied hyrohalogenation but nothing about alcohols & halogens together.

4. 1,2-dimethylcyclopentene + BH3 + H2O2/NaOH =
This gives us the same product as direct hydrolysis since the alkene is symmetrical,correct?

Any help in these questions would be greatly appreciated.They are just doubts that need clarifying :) & my exam is tomorrow.
 
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Anyone,please? :(
 
I guess I'm too late to help you for your exam. How did you do on the test? You were right about some of these.
 
ChemDoodle said:
Hey I'm studying for my chem exam & I am having difficulty solving some problems.

1. 1,3cyclohexadiene + Br2= ?
Here,should i treat it like a conjugated diene? Meaning that the Br molecules will have 1,2 and 1,4 additions on the diene and 2 products will be there?

2. 1,4cyclohexadiene + Br2 = ?
Here should i t eat it like an isolated diene? & if so..where should the Br add? On which bond? Or will there be 2 products? With Br adding on the 1 double bond in the first & 4 double bond in the second?

3. When propylene is treated with bromine in methanol (CH3OH),two products are formed C3H6Br2 & C4H9BrO.Explain meachanistically how each are formed.
Here,the first product is simple..its obtained by halogenation of alkenes..simple addition of the Br molecules on the pi-bond.But i wasn't able to determine how the second product is obtained? Obviously methanol has something to do with it..But what kind of reaction is it? We studied hyrohalogenation but nothing about alcohols & halogens together.

4. 1,2-dimethylcyclopentene + BH3 + H2O2/NaOH =
This gives us the same product as direct hydrolysis since the alkene is symmetrical,correct?

Any help in these questions would be greatly appreciated.They are just doubts that need clarifying :) & my exam is tomorrow.

1) Probably condition dependent. I have seen both 1,4 and 1,2 addition in similar cases.

2) Try drawing the mechanism, and see if you can get addition to both double bonds with one equivalent.

3) What is the intermediate in halogenation?

4) As per your previous thread, if we assume the lack of locant for the ene means it's a 1-ene. I'm not sure you get hydrolysis.
 
chemisttree said:
I guess I'm too late to help you for your exam. How did you do on the test? You were right about some of these.

86,highest grade :P I went early the next day & asked my prof about them hehe.
Thanx tho :D
 

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