CC
H
+ + X −
X H + CC
Electrophile Nucleophile
- The carbocation reacts with the halide in the next step:
CC+ X
H H
+ − CC
X
Electrophile Nucleophile
8.2 ADDITION OF HYDROGEN H LIDES TO ALKENE:
- Hydrogen halides (HI, HBr, HCl, and HF) add to the double bond of alkenes:
A
MARKOVNIKOV’S RULE
CC + HX CC
H X
- The addition reactions can be carried out:
ectly into the alkene and using the alkene itself
i) HF is prepared as polyhydrogen fluoride in pyridine.
- The order of reactivity of the HX is HI > HBr > HCl > HF:
i) Unless the alkene is highly substituted, HCl reacts so slowly that the reaction is
not an useful preparative method.
i ns are taken, the reaction may follow an
1) By dissolving the HX in a solvent such as acetic acid or CH 2 Cl 2.
2) By bubbling the gaseous HX dir
as the solvent.
i) HBr adds readily, but, unless precautio
