Virtual Lessons

Lesson 3 of 4

Electrophilic Addition Reactions of Alkenes

This virtual lesson covers the mechanisms of electrophilic addition in alkenes, explaining how the electron-rich pi bond makes alkenes highly reactive towards electrophiles.

The lesson opens by establishing why alkenes undergo addition reactions rather than substitution. The high electron density of the pi bond attracts electrophiles, which are electron-deficient species that accept electron pairs. This interaction is the basis of the electrophilic addition mechanism, drawn using curly arrow notation throughout the lesson.

A range of key reactions are then worked through, including addition of bromine (Br2) to form a dibromoalkane, and the reaction with bromine water as a test for unsaturation. Addition of hydrogen halides (HBr and HCl) is covered with application of Markovnikov's rule to predict the major product when the alkene is unsymmetrical.

The lesson also covers hydrogenation using H2 in the presence of a nickel catalyst to produce alkanes, hydration using steam (H2O(g)) and an acid catalyst to produce alcohols, and oxidation using acidified KMnO4 to produce diols, which also serves as a test for the double bond.

This lesson is central to the alkenes topic and develops the mechanistic understanding and reagent knowledge examined extensively at A-Level.