A common reagent for these allylic brominations is N-bromosuccinamide (NBS)because it continually generates small amounts of Br2 through reaction with HBr. H-Br I-H +Br-Br Other methods for Preparation (These will be covered in detail in appropriate later chapters). From alkenes and alkynes: X-x -C=C- 2H-X_ 一C=C一 2X-X Ch06 Alkyl Halides (landscape) Page 6 Ch06 Alkyl Halides (landscape) Page 6 A common reagent for these allylic brominations is N-bromosuccinamide (NBS) because it continually generates small amounts of Br2 through reaction with HBr. Other methods for Preparation (These will be covered in detail in appropriate later chapters). From alkenes and alkynes: N-Br O O + H-Br N-H O O + Br-Br C C C C C H C X H-X C C C X C X X-X C H H C X X 2 H-X C C C X X C X X 2 X-X