In which of the following, addition of HBr does not take place against Markownikoff's rule? In other words, Anti- Markownikoff's addition of HBr is not observed for
In which of the following, addition of HBr does not take place against Markownikoff's rule? In other words, Anti- Markownikoff's addition of HBr is not observed for
The correct option is C But - 2- ene
⇒ What do you mean by Markownikov's and Anti-Markownikov's reaction?
Addition of Hydrogen Halide:
Alkene on reaction with HX gives alkyl halide. This reaction occurs on dissolving the hydrogen halide in a solvent, such as acetic acid or CH2Cl2 or by bubbling the gaseous hydrogen halide directly in alkene.
The order of reactivity is give as
Hl>HBr>HCl>HF
e.g.
CH2=CH2+HBr⟶CH3−CH2−Br
CH3−CH=CH2+HBr⟶CH3−CH−CH3
|
Br
The addition of HBr in propene occurs according to Markownikoff's rule.
Mechanism:
Step-1
Step-2
The addition of HBr to propene, MeCH=CH2(1), under polar conditions (in absence of peroxide) yields 2-bromopropane. However, in the presence of peroxides or the additio proceeds via a rapid chain reaction to yield 1-bromopropane. This addition of HBr in presence of peroxide is generally referred to as the peroxide effect leading to anti-Markownikov addition. This difference in orientation of HBr addition is due to the fact that in the first (polar case) the reaction is initiated by H+ and proceeds via the more stable (secondary)carbocation while in the second (radical) case it is initiated by Br and proceeds via the more stable (secondary radical).
Chain initiation step:
→ But anti-Markownikov's rule is not applicable to symmetrical alkenes.
But - 2- ene
⇒ What do you mean by Markownikov's and Anti-Markownikov's reaction?
Addition of Hydrogen Halide:
Alkene on reaction with HX gives alkyl halide. This reaction occurs on dissolving the hydrogen halide in a solvent, such as acetic acid or CH2Cl2 or by bubbling the gaseous hydrogen halide directly in alkene.
The order of reactivity is give as
Hl>HBr>HCl>HF
e.g.
CH2=CH2+HBr⟶CH3−CH2−Br
CH3−CH=CH2+HBr⟶CH3−CH−CH3
|
Br
The addition of HBr in propene occurs according to Markownikoff's rule.
Mechanism:
Step-1
Step-2
The addition of HBr to propene, MeCH=CH2(1), under polar conditions (in absence of peroxide) yields 2-bromopropane. However, in the presence of peroxides or the additio proceeds via a rapid chain reaction to yield 1-bromopropane. This addition of HBr in presence of peroxide is generally referred to as the peroxide effect leading to anti-Markownikov addition. This difference in orientation of HBr addition is due to the fact that in the first (polar case) the reaction is initiated by H+ and proceeds via the more stable (secondary)carbocation while in the second (radical) case it is initiated by Br and proceeds via the more stable (secondary radical).
Chain initiation step:
→ But anti-Markownikov's rule is not applicable to symmetrical alkenes.
