Reaction of $HBr$ with propene in the presence of peroxide gives
- iso-propyl bromide
- 3-bromo propane
- allyl bromide
- n-propyl bromide
The Correct Option is D
Approach Solution - 1
Reaction of HBr with propene in the presence of peroxide gives n-propyl bromide. This addition reaction is an example of anti-Markownikoffs
addition reaction. (i.e. it is completed in form of free radical addition) \(CH_3-CH =CH_2 +HBr \xrightarrow{Peroxide}\) \(\hspace50mmCH_3-CH_2-CH_2Br\) \(\hspace50mm _{}^{\, \, \, \, \, \, \, n-propyl\, bromide}\) Mechanism of this reaction is represented as follows:
Step II Benzoate free radical forms bromine free radical with HBr.
\(C_6 H_5 CO \mathring{O}+H-Br \longrightarrow C_6 H_5 COOH +B \mathring{r}\) free radical from benzoic acid and give final product of reaction.
\(CH_3 - \mathring{C}H-CH_2 Br + C_6 H_5 COOH \longrightarrow\)
\(\hspace20mm CH_3 - CH_2-CH_2 Br + C_6 H_5 CO \mathring{O}\)
\(\hspace20mm _{}^{n-propyl\, bromide}\)
Step V Benzoate free radicals are changed into benzoyl peroxide for the termination of free radical chain.
\(C_6 H_5 CO \mathring{O}+C_6 H_5 CO \mathring{O} \longrightarrow (CC_6 H_5 CO)_2 O_2\)
Read more from the chapter: Haloalkanes and Haloarenes
Approach Solution -2
The Correct Answer is (D)
Real Life Applications
The reaction of HBr with propene in the presence of peroxide gives 2-bromopropane. The real life applications are:
- Production of plastics.
- 2-bromopropane is used as fire retardant.
- It is highly used in pharmaceuticals.
Question can also be asked as
- What is the product of the reaction of HBr with propene in the presence of peroxide?
- How does the presence of peroxide affect the reaction of HBr with propene?
- What is the mechanism of the reaction of HBr with propene in the presence of peroxide?
Approach Solution -3
The Correct Answer is (D)
When an electrophile HX reacts with an alkene, the bond of the hydrogen atom will be formed at the beginning of the alkyne. This is to ensure that there is a minimum amount of hydrogen atoms. Alkenes are unsaturated hydrocarbons and have at least one double bond.
Anti-Markonikov Addition
When we talk about the Markonikov rule, If there is an unsymmetrical alkene, HBr in the presence of hydrogen peroxide. There is production of 1-bromopropane is produced in place of 2-bromopropane. This reaction is also called the anti-Markovnikov addition or the Kharash effect. It is also called as peroxide effect.
Mechanism of Anti-Markovnikov Addition
- There is a homolytic cleavage of peroxide. This produces free radicals.
- The free radicle will attack hydrogen halide and form halide radicals.
- The halide radicals produced will attack the alkene, and form alkyl radicals.
- Thus alkyl halide will be formed due to the homolytic breakage of hydrogen halide.
Read more:
| Related Concepts | ||
|---|---|---|
| Peroxide | Electrophilic | Halogenation |
| Carbon | Hydrogen peroxide | Huckel rule |
Top Questions on Alkenes
An alkene X (\( C_4H_8 \)) on reaction with HBr gave Y (\( C_4H_9Br \)). Reaction of Y with benzene in the presence of anhydrous \( AlCl_3 \) gave Z which is resistant to oxidation with \( KMnO_4 + KOH \). What are X, Y, Z respectively?
Which of the following alkenes is most stable?
- The chemical name of calgon is:
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- An alkene X (\( C_4H_8 \)) does not exhibit cis-trans isomerism. Reaction of X with \( Br_2 \) in the presence of UV light gave Y. What is Y?
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Concepts Used:
Alkenes
Alkenes
In organic chemistry, an alkene is a hydrocarbon containing a carbon-carbon double bond.[1]
Alkene is often used as synonym of olefin, that is, any hydrocarbon containing one or more double bonds.
Read More: Ozonolysis
IUPAC Nomenclature of Alkenes
- An alkene or cycloalkene is indicated by the suffix (ending) ene.
- For the root name, the longest chain must include both carbon atoms of the double bond.
- The root chain must be numbered beginning at the end closest to a double bond carbon atom. If the double bond is in the chain's centre, the nearest substituent rule is used to determine where the numbering begins.
- If the compound contains more than one double bond, it is named with a diene, triene, or equivalent prefix indicating the number of double bonds, and each double bond is assigned a locator number.
Read More: Unsaturated Hydrocarbon