Advertisements
Advertisements
प्रश्न
Explain. Aryl halides are less reactive than alkyl halides towards nucleophilic substitution reactions.
Advertisements
उत्तर
- The low reactivity of aryl halides is due to the resonance effect and sp2 hybrid state of carbon to which halogen atom is attached.
- In aryl halides, one of the lone pairs of electrons on the halogen atom is in conjugation with π-electrons of the ring. Due to resonance, the C–X bond acquires partial double bond character. Thus, the C–X bond in aryl halides is stronger and shorter than alkyl halides. Hence, it is difficult to break C–X bond in aryl halides.
- Further, the phenyl cation produced due to the self-ionization of aryl halide will not be stabilised by resonance. This rules out the possibility of SN1 mechanism. Also, the backside attack of nucleophiles is blocked by the aromatic ring. This rules out the possibility of SN2 mechanism. As a result, nucleophilic substitution reaction involving cleavage of C–X bond in haloarenes proceeds with difficulty.
- Therefore, aryl halides are less reactive than alkyl halides towards nucleophilic substitution reactions.
संबंधित प्रश्न
from the following pair would undergo SN2 faster from the other?
a. CH3CH2CH2I b. CH3CH2CH2Cl
Name the reagent used to bring about the following conversion.
Chlorobenzene to biphenyl
Arrange the following in the increasing order of boiling points.
- 1-Bromopropane
- 2- Bromopropane
- 1- Bromobutane
- 1-Bromo-2-methylpropane
Give reasons:
Haloarenes are less reactive than haloalkanes.
Distinguish between SN1 and SN2 mechanism of substitution reaction.
Convert the following:
Propene to propan-1-ol
Convert the following:
Benzyl alcohol to benzyl cyanide
Convert the following:
tert-Butyl bromide to isobutyl bromide
Propane nitrile can be prepared by heating ____________
The following will react faster by SN1 mechanism
Write the correct order of increasing ease of dehydrohalogenation.
\[\ce{\underset{\text{(I)}}{CH3 - CH2 - CH2 - Cl}}\]
\[\ce{\underset{\text{(II)}}{CH3 - CH(Cl) - CH3}}\]
\[\begin{array}{cc}
\ce{CH3}\\
|\\
\ce{CH3-C-Cl}\phantom{...}\\
|\\
\ce{CH3}\\
\ce{(III)}
\end{array}\]
Explain aqueous alkaline hydrolysis of tert. butyl bromide.
Which of the following is a primary halide?
Ethyl bromide undergoes the following reaction:
\[\ce{\underset{Ethyl bromide}{C2H5Br} + \underset{(aq.)}{KOH} ->[\Delta] \underset{Ethyl alcohol}{C2H5OH} + KBr}\]
Which of the following is a WRONG statement?
Dehydrohalogenation of an alkyl halide is ____________.
Nitroalkanes are obtained in laboratory from primary or secondary alkyl halides by the action of ______.
How many metameric ethers are represented by the molecular formula C4H10O?
What type of hybridisation is present in carbocation formed during the alkaline hydrolysis of 1- bromo-1- phenyl ethane?
When C2H5Br is treated with excess of alc. NH3, the major product obtained is ____________.
The SN2 reaction of a compound containing an asymmetric carbon atom always gives ____________.
The order of reactivities of the following alkyl halides for an SN2 reaction is ______.
Which of the following statements is incorrect regarding the dehydrohalogenation of alkenes?
The order of reactivity of the given haloalkanes towards nucleophiles is:
Explain the dehydrohalogenation reaction of 2-chlorobutane.
Complete the following reaction giving major products.
\[\begin{array}{cc}
\ce{CH3}\phantom{.......}\\
|\phantom{.........}\\
\ce{CH3 - c - CH2 - Cl ->[Na/dry ether]}\\
|\phantom{.........}\\
\ce{CH3}\phantom{.......}
\end{array}\]
Observe the following and answer the question given below:
Comment on the bond length of C-X bond in it.
Complete the reaction:
\[\ce{CH3CH2Cl ->[AgCN][alc.\Delta]}\] ?
Complete the following reaction giving major product.
\[\begin{array}{cc}
\ce{CH3}\phantom{.................}\\
|\phantom{...................}\\
\ce{CH3 - C - CH2 - Cl ->[Na/dry ether] A}\\
|\phantom{...................}\\
\ce{CH3}\phantom{.................}
\end{array}\]
Give a reason for the following:
Ethoxy ethane with conc. HI at 373 K gives C2H5OH and CH3I but not CH3OH and C2H5I.
