Learning objective

Explain carbocation formation and stability where appropriate.

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Topic

Alkenes

Subtopic

Electrophilic addition

AQA A Level ChemistryOrganic chemistry

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Understand this objective

Short explanation

Carbocations are positively charged species formed during electrophilic addition reactions involving alkenes. When an alkene reacts with an electrophile, the π bond is broken, leading to the formation of a carbocation intermediate. The stability of a carbocation is influenced by the surrounding groups; tertiary carbocations are more stable than secondary, which are more stable than primary, due to hyperconjugation and inductive effects. This stability affects the reaction pathway and the major product formed. Understanding carbocation stability is crucial for predicting the outcomes of reactions involving alkenes.

Key concepts

alkenecarbocation

Why it matters

This objective helps connect Electrophilic addition to exam-style questions, flashcards, and revision notes for Alkenes.

Common mistakes

1 linked

Misunderstanding Carbocation Stability: To explain carbocation stability, remember that tertiary carbocations are more stable than secondary, which are more stable than primary. This is due to the inductive effect and hyperconjugation from surrounding alkyl groups. For example, a tertiary carbocation (R3C+) is stabilized by three alkyl groups donating electron density, while a primary carbocation (RCH2+) is only stabilized by one. Thus, when predicting the major product of an electrophilic addition reaction, consider the stability of the carbocation formed during the reaction.

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