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प्रश्न
Which would undergo SN1 reaction faster in the following pair and why?
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उत्तर १
Carbocations are the intermediates in the SN1 reaction. Greater the stability of the carbocations, more easily will the product be formed and hence faster will be the rate of the reaction. Because the stability of the carbocations decreases in the order: 3° carbocation > 2° carbocation > 1° carbocation > CH3+.
Therefore, the reactivity of alkyl halides towards SN1 reactions decreases in the same order, i.e. 3° alkyl halides > 2° alkyl halides > 1° alkyl halides > methyl halides.
The two structures are
Bromoethane is a primary alkyl halide which forms a 1° carbocation intermediate in the SN1 reaction. The other compound is 2-bromo-2-methylpropane which is a tertiary alkyl halide which forms a tertiary carbocation intermediate in the SN1 reaction. Hence, 2-bromo-2-methylpropane undergoes an SN1 reaction faster than bromoethane
उत्तर २
A tertiary alkyl halide tends to undergo the SN1 mechanism because it can form a tertiary carbocation, which is stabilised by the three alkyl groups attached to it. As alkyl groups are electron donating, they allow the positive charge in the carbocation to be delocalised by the induction effect. Hence, out of the given pairs, (CH3)3C-Br would undergo SN1 reaction faster than CH3-CH2-Br.
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संबंधित प्रश्न
In the following pair of halogen compounds, which compound undergoes a faster SN1 reaction?
In the following pair of halogen compounds, which compound undergoes a faster SN1 reaction?
Write the mechanism of the following reaction:
\[\ce{{n}BuBr + KCN ->[EtOH-H2O] {n}BuCN}\]
Among the following, the dissociation constant is highest for:
The reaction of C6H5–CH=CH–CH3 with HBr produces:
The increasing order of reactivity towards SN1 mechanism is:
(I) \[\begin{array}{cc}
\ce{CH3-CH-CH2-CH3}\\
|\phantom{........}\\
\ce{CH3}\phantom{.....}
\end{array}\]
(II) CH3CH2CH2Cl
(III) P–CH3O–C6H4–CH2Cl
Complete the following analogy:
Same molecular formula but different structures: A : : Non superimposable mirror images: B
Match the reactions given in Column I with the types of reactions given in Column II.
| Column I | Column II | |
| (i) |  |
(a) Nucleophilic aromatic substitution |
| (ii) | \[\begin{array}{cc} \ce{CH3 - CH = CH2 + HBr -> CH3 - CH - CH3}\\ \phantom{............................}|\phantom{}\\ \phantom{.............................}\ce{Br}\phantom{} \end{array}\] |
(b) Electrophilic aromatic substitution |
| (iii) |  |
(c) Saytzeff elimination |
| (iv) |  |
(d) Electrophilic addition |
| (v) | \[\begin{array}{cc} \ce{CH3 CH2 CH CH3 ->[alc.KOH] CH3 CH = CH CH3}\\ \phantom{}|\phantom{..........................}\\ \phantom{}\ce{Br}\phantom{........................} \end{array}\] |
(e) Nucleophilic substitution (SN1) |
In SN1 reactions, the correct order of reactivity for the following compounds:
CH3Cl, CH3CH2Cl, (CH3)2CHCl and (CH3)3CCl is ______.
The decreasing order of reactivity of the following compounds towards nucleophilic substitution (SN2) is ______.
