Reactions of Alkynes:Addition of HX and X2 Addition reactions of alkynes are similar to those of alkenes Intermediate alkene reacts further with excess reagent Regiospecificity according to Markovnikov's Rule Br H Br H CH CHCH2CH2C=CH HBr CH2CO2H CH CH2CH2CH,C=CH HBr CH CH2CH2CH2C-C-H 1-Hexyne 2-Bromo-1-hexene Br H 2,2-Dibromohexane CH,CH CH CH2C=CCH2CH HCI.NH CI C=C CH3CO2H 3-Hexyne CH,CH2 H (Z)-3-Chloro-3-hexene (95%)
Reactions of Alkynes: Addition of HX and X 2 Addition reactions of alkynes are similar to those of alkenes Intermediate alkene reacts further with excess reagent Regiospecificity according to Markovnikov’s Rule
R R H Br H-Br :Br:- +0 H H H An alkene An alkyl carbocation An alkyl bromide H Br H :Br: RC=CH R一 H R H An alkyne A vinylic carbocation A vinylic bromide 2004 Thomson-Brooks/Cole