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Ch. 9 - Alkenes II: Oxidation and Reduction
Mullins - Organic Chemistry: A Learner Centered Approach 1st Edition
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471Not the one you use?Change textbook
All textbooksMullins 1st EditionCh. 9 - Alkenes II: Oxidation and ReductionProblem 45l(i,ii)
Chapter 8, Problem 45l(i,ii)

Predict the product(s) that would result when the alkenes are allowed to react under the following conditions: (i) Br2 (ii) Cl2
(l)

Verified step by step guidance
1
Step 1: Analyze the structure of the given alkene. The molecule contains a double bond, which is the reactive site for halogenation reactions. The double bond is located between two carbon atoms, making it susceptible to electrophilic addition reactions.
Step 2: Understand the reaction conditions. (i) Br₂ and (ii) Cl₂(l) are halogenation reagents. These reagents react with alkenes via an electrophilic addition mechanism, where the halogen molecule adds across the double bond.
Step 3: Describe the mechanism. When Br₂ or Cl₂ reacts with the alkene, the π-electrons of the double bond attack the halogen molecule, forming a cyclic halonium ion intermediate. This intermediate is then attacked by the halide ion (Br⁻ or Cl⁻), leading to the formation of a vicinal dihalide (two halogen atoms added to adjacent carbons).
Step 4: Consider stereochemistry. The addition of halogens to the double bond occurs in an anti-addition manner due to the geometry of the halonium ion intermediate. This means the two halogen atoms will be added to opposite faces of the double bond, resulting in stereoisomers.
Step 5: Predict the product(s). For reaction (i) with Br₂, the product will be a vicinal dibromide. For reaction (ii) with Cl₂(l), the product will be a vicinal dichloride. Both products will exhibit anti-addition stereochemistry, and the specific stereoisomers formed will depend on the spatial arrangement of the substituents around the double bond.

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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 are a fundamental type of reaction for alkenes, where an electrophile reacts with the double bond of the alkene. This process involves the formation of a carbocation intermediate, which can lead to the addition of various nucleophiles. Understanding this mechanism is crucial for predicting the products when alkenes react with halogens like Br₂ and Cl₂.
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Halogenation of Alkenes

Halogenation is the addition of halogen molecules (such as Br₂ or Cl₂) to alkenes, resulting in the formation of vicinal dihalides. This reaction typically proceeds through a cyclic halonium ion intermediate, which influences the stereochemistry of the product. Recognizing the stereochemical outcomes is essential for accurately predicting the products of the reaction.
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Regioselectivity and Stereochemistry

Regioselectivity refers to the preference of a chemical reaction to yield one structural isomer over others, while stereochemistry deals with the spatial arrangement of atoms in molecules. In the context of halogenation of alkenes, understanding how these factors influence the formation of products is vital, as they determine whether the addition occurs in a syn or anti manner, affecting the final product's configuration.
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Related Practice
Textbook Question

Predict the product(s) that would result when the alkenes are allowed to react under the following conditions: (i) Br2

(k)

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Textbook Question

Predict the product(s) that would result when the alkenes are allowed to react under the following conditions: (vii) 1. mCPBA 2. H2SO4, H2O (viii) 1. O3 2. CH3SCH3

(l)

1
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Textbook Question

Predict the product(s) that would result when the alkenes are allowed to react under the following conditions: (vii) 1. mCPBA 2. H2SO4, H2O

(k)

2
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Textbook Question

Predict the product(s) that would result when the alkenes are allowed to react under the following conditions: (ix) H2, Pd/C; and (x) D2, Pd/C.

(l)

Textbook Question

Predict the product(s) that would result when the alkenes are allowed to react under the following conditions: (iii) Br2, H2O ; (iv) Cl2, CH3OH;

(l)

1
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Textbook Question

Predict the product(s) that would result when the alkenes are allowed to react under the following conditions: (v) mCPBA; (vi) 1. OsO4 2. NaHSO3 

(l)

5
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