Alkynes比 Alkenes的亲电反应活性低 e.g. CH2-CH-CH2-C=CH+ Br2 CH2-CH-CH2-C=CH Br Br -penten-4-yne 4, 5-dibromo-1-pentyne Stability of carbocations: All, Benzyl>3°>2°>1°> Vinyl>CH3 CH2-C+=CH Br 乙烯基碳正离子 (Vinylic cation)Alkynes 比 Alkenes 的亲电反应活性低. e.g. CH2 =CH-CH2 -CCH + Br2 CH2 -CH-CH2 -CCH Br Br 1-penten-4-yne 4,5-dibromo-1-pentyne Stability of Carbocations: Allyl , Benzyl > 3°> 2°>1°> Vinyl > CH3 + 乙烯基碳正离子 (Vinylic cation) CH3 - C+ = CH Br