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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
from the following pair would undergo SN2 faster from the other?
a. 
b. 
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tert-Butyl bromide to isobutyl bromide
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\[\ce{2-Bromobutane->[Alc.KOH]A->[][Br2]B->[][NaNH2]C}\]
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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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\[\ce{NO2_{(g)} + F2_{(g)} -> NO2F_{(g)} + F_{(g)} (slow)}\]
\[\ce{F_{(g)} + NO2_{(g)} -> NO2F_{(g)} (fast)}\]
The order of the reaction with respect to NO2(g)
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\[\ce{But-1-ene ->[HBr][Peroxide] A ->[AgCN][\Delta] B}\]
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\[\begin{array}{cc}
\ce{CH3}\phantom{...............}\\
|\phantom{..................}\\
\ce{CH3 - C - CH2 - Cl->[Na/dry ether]A}\\
|\phantom{..................}\\
\ce{CH3}\phantom{...............}\\
\end{array}\]
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alcoholic sodium hydroxide
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\[\ce{CH3CH2Cl ->[AgCN][alc.\Delta]}\] ?
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.
Complete the following reaction giving major product.
\[\begin{array}{cc}
\ce{CH3}\phantom{.................}\\
|\phantom{...................}\\
\ce{CH3 - C - CH2 - Cl ->[Na/dry ether] A}\\
|\phantom{...................}\\
\ce{CH3}\phantom{.................}\\
\end{array}\]
