Reactions at the Allylic Position: Study with Video Lessons, Practice Problems & Examples
Created using AIAllylic compounds exhibit unique reactivity due to the stability of allylic carbocations, which are stabilized by resonance, making them more reactive in SN1 and E1 reactions compared to alkyl counterparts. Allylic anions are more acidic than alkyl anions, leading to increased elimination products. In radical reactions, allylic halogenation occurs when halogens replace allylic protons, facilitated by radical initiators. Additionally, allylic oxidation selectively transforms allylic alcohols into carbonyls using manganese(IV) oxide, preserving the alkene double bond. Understanding these reactions is crucial for mastering organic synthesis and reaction mechanisms.
Reactions at the Allylic Position Concept 1
Reactions at the Allylic Position Concept 2
Reactions at the Allylic Position Example 1
Which of the following alcohols will undergo acid-catalyzed dehydration at the fastest rate?
What are the substitution products of the following reaction?
Reactions at the Allylic Position Concept 3
Reactions at the Allylic Position Example 2
Which of the following compounds will undergo E2 elimination at the fastest rate?
I
II
Both will proceed at equal rates.
Reactions at the Allylic Position Concept 4
Reactions at the Allylic Position Example 3
Draw the structures of the compounds A and B for the following synthesis.
Reactions at the Allylic Position Concept 5
Reactions at the Allylic Position Example 4
Reactions at the Allylic Position Concept 6
Reactions at the Allylic Position Example 5
Draw the structures of products A and B for the given reactions.
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More setsHere’s what students ask on this topic:
What is the allylic position in organic chemistry?
The allylic position in organic chemistry refers to the carbon atom adjacent to a double bond. This position is significant because it exhibits unique reactivity due to the stability provided by resonance. For example, in a molecule with a double bond between two carbons (C=C), the carbon atoms directly attached to these double-bonded carbons are in the allylic position. This position is more reactive in certain reactions, such as SN1, E1, and radical reactions, compared to non-allylic positions.
Created using AIWhy are allylic carbocations more stable than alkyl carbocations?
Allylic carbocations are more stable than alkyl carbocations due to resonance stabilization. In an allylic carbocation, the positive charge can be delocalized over multiple atoms through resonance structures. This delocalization distributes the charge more evenly, reducing the energy of the carbocation and increasing its stability. In contrast, alkyl carbocations are primarily stabilized by hyperconjugation, which is less effective than resonance.
Created using AIHow do allylic anions differ from alkyl anions in terms of acidity?
Allylic anions are more acidic than alkyl anions because the conjugate base of an allylic anion is resonance-stabilized. When a proton is removed from the allylic position, the resulting negative charge can be delocalized over multiple atoms through resonance. This stabilization lowers the pKa of the allylic proton, making it more acidic compared to an alkyl proton, which lacks such resonance stabilization.
Created using AIWhat is allylic halogenation and how does it occur?
Allylic halogenation is a reaction where a halogen replaces an allylic hydrogen atom. This process is facilitated by radical initiators such as heat, UV light, or peroxides. For example, using N-bromosuccinimide (NBS) in the presence of UV light can selectively brominate the allylic position. The reaction involves the formation of a radical intermediate, which allows the halogen to replace the allylic hydrogen, resulting in an allylic halide.
Created using AIWhat is the role of manganese(IV) oxide in allylic oxidation?
Manganese(IV) oxide (MnO2) is used as an oxidizing agent in allylic oxidation to selectively oxidize allylic alcohols to carbonyl compounds. This reaction occurs without affecting the alkene double bond. For instance, an allylic alcohol can be converted to an allylic ketone or aldehyde using MnO2 in a methylene chloride solvent. This selective oxidation is useful in organic synthesis for transforming specific functional groups while preserving others.
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