Illustrated Glossary of Organic Chemistry

N-Chlorosuccinimide (NCS): A reagent useful for allylic and benzylic chlorination, while at the same time, avoiding electrophilic addition of chlorine to a pi bond. The reaction mechanism involves a free radical pathway, and usually requires a radical chain initiator such as a peroxide.

Molecular structure of N-chlorosuccinimide.

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Use of NCS for allylic chlorination of cyclohexene.