The reaction of 2-methylnorborn-2-ene with N-bromosuccinimide produced exo-3bromo-2-methylenenorbornane and 2-methyl-3-bromonortricyclene in a 3 : 1 ratio. No 2-bromomethyl-norborn-2-ene was found. Most of the unreacted olefin was found to be isomerized to 2methylenenorbornane.The hydrolysis of 2-methyl-3-bromo-nortricyclene with silver acetate in a 50 yo mixture of acetone and water afforded the corresponding alcohol and acetate. Exo-3-bromo-2-methylenenorbornane on similar treatment gave the exo-3-hydroxy-2-methylene-norbornane and 2-hydroxymethyl-norbornane and 2-hydroxymethyl-norborn-2-ene and their corresponding acetates in a 3: 2 ratio.An ionic rather than a radical mechanism is proposed for the bromination reaction. In the solvolysis reactions of the resulting bromides the nature of the ionic intermediates is discussed.Introduction, -The behaviour of N-bromosuccinimide (NBS) as a brominating agent towards bridged bicyclic olefins is capricious. When the allylic C-H bond lies in the nodal plane of the double bond, reactivity is usually directed towards the homoallylic position or the double bond itself [Z]. When an allylic position is available, bromination is thought to proceed via allylic radicals which subsequently give the corresponding endocyclic allylic bromides (31.As 2-methylnorborn-2-ene contains both these structural elements, its reactivity is of crucial interest. Furthermore, the properties of the bromides obtained relate to the problem of the nature of bridged cations.Results. -2-Methylnorborn-2-ene (I) and N-bromosuccinimide were allowed to react in boiling carbontetrachloride containing benzoyl peroxide. The resulting products were identified as exo-3-bromo-2-methylene-norbornane (II), 3-bromo-%methylnortricyclene (111) and 2-methylenenorbornane (IV). The structures of I1 and 111 were assigned from a consideration of their NMR. and IR. spectra. The exo assignment of the bromine at C-3 in I1 was made on the basis of the magnitude of the coupling constant exhibited for C-3-H, (3J N 1.8 Hz) ; a larger value (ca. 4 Hz) would l) Address inquiries to the