Textbook Question
What is the major product of each of the following reactions?
a.
10. Addition Reactions
Hydrohalogenation
5:02 minutesProblem 87g
Textbook Question
Draw the products of the following reactions. If the products can exist as stereoisomers show what stereoisomers are formed.
g. 3,3-dimethyl-1-pentene + HBr
Verified step by step guidance1
Identify the type of reaction: The reaction involves an alkene (3,3-dimethyl-1-pentene) reacting with HBr. This is an electrophilic addition reaction, where the π-bond of the alkene reacts with the electrophile (HBr).
Determine the regioselectivity: According to Markovnikov's rule, the hydrogen (H⁺) from HBr will add to the carbon of the double bond that has more hydrogens already attached, while the bromine (Br⁻) will add to the carbon with fewer hydrogens.
Draw the carbocation intermediate: After the hydrogen adds to the less substituted carbon of the double bond, a carbocation forms on the more substituted carbon. Check for the possibility of carbocation rearrangement, but in this case, the carbocation is already tertiary and stable, so no rearrangement occurs.
Add the nucleophile: The bromide ion (Br⁻) will attack the carbocation, forming the final product. Since the carbocation is planar, the attack can occur from either side, potentially leading to the formation of stereoisomers if a chiral center is created.
Analyze stereochemistry: Check if the product contains a chiral center. If it does, draw both possible stereoisomers (R and S configurations) and label them accordingly. If no chiral center is formed, the product will not have stereoisomers.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Electrophilic Addition Reactions
Electrophilic addition reactions involve the addition of an electrophile to a nucleophile, typically seen in alkenes. In this case, HBr acts as the electrophile, adding across the double bond of 3,3-dimethyl-1-pentene. This reaction results in the formation of a more stable carbocation intermediate, which influences the final product distribution.
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Carbocation Stability
Carbocation stability is crucial in determining the outcome of electrophilic addition reactions. Tertiary carbocations are more stable than secondary or primary ones due to hyperconjugation and inductive effects. In the reaction of 3,3-dimethyl-1-pentene with HBr, the formation of a tertiary carbocation leads to the preferential formation of products that can arise from this stable intermediate.
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Stereoisomerism
Stereoisomerism occurs when molecules have the same molecular formula and connectivity but differ in the spatial arrangement of atoms. In the context of the reaction between 3,3-dimethyl-1-pentene and HBr, the addition of HBr can lead to the formation of chiral centers, resulting in the production of stereoisomers. Identifying and drawing these stereoisomers is essential for a complete understanding of the reaction products.
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