Summary Alkene mechanisms

Page # 1
Addition of H-X to an Alkene - Electrophilic Addition Reaction

Possibility # 1



H H
H
protonation CHz cuz
H C H
C C notformed toounstable
H
H H

Possibility # 2

H
ABr protonation



H
CH
Regioselective:
YES
4
mayoknewnioknfinitionaleisomer
issavored
Stereoselective: NO
nucleophilic Br
Carbocation Rearrangement: YES attack

Reaction Summary:
Step1 PROTONATION aBoor
It goes to carbon of doublebond with mostprotons
Step 2 NUCLEOPHILIC ATTACK

x goestothemostcarbocation like carbocation followingcarbocation
rearrangement it necessary
the halogengetsadded on to the more substitutedcarbon
Product




Example:



+ HCl CII

, Page # 2
Acid Catalyzed Hydration of an Alkene
O H O


H O S O H
+f O proton
O + O S O H
H H transfer
O
µ H H
O



H

H C H protonation zo H2O
C C
H
H

y H




H
GO
H



H
nucleophilic
attack
4 H O H




oo H H
iOH H O H I
0
I
deprotonation
I Oxonium
ion
Product


Reaction Summary:
Step 1 protonation of alkene to generate more stable
electrophilic carbocation
moleculeon
Step 2 attackof thenucleophilicH2O
createsan oxoniumion
Regioselectivity:
YES Markovnikov
alcohol
step3 deprotonation by abasegeneratesthe
OHGOESONMORE SUBSTITUTEDCARBON
FOLLOWSMARKOVNIKOV Stereoselectivity:NO racemic mixture
RACEMICMIXTURE FORMED IF THERE'S ACHIRALCENTER
Example: Carbocation Rearrangement:YES
OH
Cat H 2SO 4
N
H 2O racemic