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प्रश्न
Explain primary benzylic halide shows higher reactivity by SN1 mechanism than other primary alkyl halide.
उत्तर
- SN1 reaction involves the formation of a carbocation intermediate. The benzylic carbocation intermediate formed are resonance stabilized, and hence SN1 mechanism is favoured.
- Resonance stabilization of benzylic carbocation can be represented as:
- Reactivity order of alkyl halides towards SN1 mechanism is 3° > 2° > 1° > CH3X. That is, SN1 mechanism is least favoured in primary alkyl halides.
- Benzylic carbocation formed is more stable than the primary carbocation; therefore, primary benzylic halide shows higher reactivity by SN1 mechanism than other primary alkyl halide.
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संबंधित प्रश्न
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\[\begin{array}{cc}\ce{CH3 - CH - CH3 ->[Red P/Br2] A ->[Ag2O/H2O]B}\\|\phantom{.........................}\\
\ce{OH\phantom{.......................}}\end{array}\]
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Ethyl bromide to ethyl isocyanide
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Chlorobenzene to biphenyl
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- 1-Bromopropane
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The following will react faster by SN1 mechanism
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\[\ce{CH3-CH2-Mg-Br + NH3 ->?}\]
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\[\ce{\underset{\text{(I)}}{CH3 - CH2 - CH2 - Cl}}\]
\[\ce{\underset{\text{(II)}}{CH3 - CH(Cl) - CH3}}\]
\[\begin{array}{cc}
\ce{CH3}\\
|\\
\ce{CH3-C-Cl}\phantom{...}\\
|\\
\ce{CH3}\\
\ce{(III)}
\end{array}\]
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\[\begin{array}{cc}
\ce{CH3}\phantom{.......}\\
|\phantom{.........}\\
\ce{CH3 - c - CH2 - Cl ->[Na/dry ether]}\\
|\phantom{.........}\\
\ce{CH3}\phantom{.......}
\end{array}\]
Complete the following reactions giving a major product.
\[\begin{array}{cc}
\ce{CH3}\phantom{................}\\
|\phantom{..................}\\
\ce{CH3 - C - CH2 - Cl ->[Na/dry ether] A}\\
|\phantom{..................}\\
\ce{CH3}\phantom{................}
\end{array}\]
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Complete the following reaction giving major product.
\[\begin{array}{cc}
\ce{CH3}\phantom{...............}\\
|\phantom{..................}\\
\ce{CH3 - C - CH2 - Cl ->[Na/dry ether]A}\\
|\phantom{...................}\\
\ce{CH3}\phantom{.................}
\end{array}\]
Complete the following reaction giving major product.
\[\begin{array}{cc}
\ce{CH3}\phantom{................}\\
|\phantom{..................}\\
\ce{CH3 - C - CH2 - Cl ->[Na/dry ether]A}\\
|\phantom{..................}\\
\ce{CH3}\phantom{................}
\end{array}\]
