Advertisements
Advertisements
प्रश्न
Why are aryl halides less reactive towards nucleophilic substitution reactions than alkyl halides?
Why are aryl halides less reactive than alkyl halides towards nucleophilic substitution reactions?
Why are haloarenes less reactive towards nucleophilic substitution reactions as compared to haloalkanes?
Advertisements
उत्तर
Aryl halides are less reactive towards nucleophilic substitution reaction due to the following reasons.
- In haloarenes, the lone pair of electron on halogen are in resonance with benzene ring. So, C – Cl bond acquires partial double bond character which strengthen C – Cl bond and difficult to be substituted by nucleophile.
Therefore, they are less reactive towards nucleophilic substitution reaction.
- In haloarenes, the carbon atom attached to halogen is sp2 hybridised. The sp2 hybridised carbon is more electronegative than sp3 hybridised carbon. This sp2-hybridised carbon in haloarenes can hold the electron pair of \[\ce{C - X}\] bond more tightly and make this \[\ce{C - Cl}\] bond shorter than \[\ce{C Cl}\] bond of haloalkanes.
Since, it is difficult to break a shorter bond than a longer bond, therefore, halorenes are less reactive than haloalkanes. - In haloarenesm the phenyl cation is not stabilised by resonance therefore SN1 mechanism cannot be followed.
- Because of the repulsion between the nucleophile and electron-rich arenas, aryl halides are less reactive than alkyl halides.
APPEARS IN
संबंधित प्रश्न
Which alkyl halide from the following pair would you expect to react more rapidly by an SN2 mechanism? Explain your answer.
CH3CH2CH2CH2Br or \[\begin{array}{cc}
\ce{CH3CH2CHCH3}\\
\phantom{...}|\\
\phantom{....}\ce{Br}\
\end{array}\]
Write the structure of the major organic product in the following reaction:
\[\ce{CH3CH(Br)CH2CH3 + NaOH ->[water]}\]
C–Cl bond length in chlorobenzene is shorter than C–Cl bond length in CH3–Cl.
Which would undergo SN2 reaction faster in the following pair and why ?
CH3 – CH2 – Br and CH3 – CH2 – I
What is the action of the following on ethyl bromide
alcoholic solution of potassium hydroxide.
What is the action of the following on ethyl bromide?
silver acetate
Answer the following question.
Write one stereochemical difference between SN1 and SN2 reactions.
Arrange the following organic compounds in descending order of their reactivity towards SN1 reaction.
C6H5CH2Br, C6H5CH(C6H5)Br, C6H5CH(CH3)Br, C6H5C(CH3)(C6H5)Br
In the SN1 reaction, racemization takes place. It is due to:
Optically active isomers but not mirror images are called ____________.
Which of the following is the correct order of decreasing SN2 reactivity?
The reaction of C6H5–CH=CH–CH3 with HBr produces:
Give reason for the following:
The product formed during SN1 reaction is a racemic mixture.
Among the following compounds I - IV, which one forms a yellow precipitate on reacting sequentially with (i) NaOH (ii) dil. HNO3 (iii) AgNO3?
 |
 |
 |
 |
| I | II | III | IV |
Racemisation occurs in ______.
Assertion (A) : Nucleophilic substitution of iodoethane is easier than chloroethane.
Reason (R) : Bond enthalpy of C-I bond is less than that of C-Cl bond.
Convert bromoethane to propanamine.
