Consider the following reactions, which are carried out at the same temperature.
$C H_{3} - B r + O H^{⊖} E t O H ⟶ C H_{3} - O H + B r^{⊖} . . . (i) C H_{3} - B r + O H^{⊖} D M S O ⟶ C H_{3} - O H + B r^{⊖} . . . (i)$
Which of the following statement is correct about these reactions?

Both the reactions take place at the same rate

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The first reaction takes place faster than second reaction.

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The second reaction takes place faster than first reaction.

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Both the reactions take place by

S_{N} 1

Mechanism

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Solution

The correct option is C The second reaction takes place faster than first reaction.
$O H^{-}$ is a strong nucleophile and the substrate is primary alkyl halide so the given reaction readily undergo $S_{N} 2$ reaction.
Polar aprotic solvent favours $S_{N} 2$ mechanism because polar aprotic solvent is unable to solvate the nucleophile.
So, the nucleophilicity of a nucleophile does not decrease in polar aprotic solvent.
DMSO is polar aprotic solvent and ethanol is a polar protic solvent.
Ethanol will solvate the $O H^{-}$ and reduce its nucleophilicity
Hence, the second reaction takes place faster than first reaction.

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Similar questions

C H_{3} B r + O H^{-} C_{2} H_{5} O H - ---- \to C H_{3} O H + B r^{-}

C H_{3} B r + O H^{-} (C H_{3})_{2} S O - ----- \to C H_{3} O H + B r^{-}

C H_{3} B r + O H^{-} C_{2} H_{5} O H - ---- \to C H_{3} O H + B r^{-}

C H_{3} B r + O H^{-} (C H_{3})_{2} S O - ----- \to C H_{3} O H + B r^{-}

C H_{3} - C H_{2} - B r + N a O H_{1} C H_{3} - C H_{2} - O H + N a B r \to

(1)

C H_{3} - C H_{3} | C | C H_{3} - C H_{2} - B r + N a O H_{2} (C H_{3})_{3} C - C H_{2} - O H + N a B r \to

(2)

K_{1}

K_{2}

Which of the following is the example of SN² reaction

[CPMT 1999]

C H_{3} - B r + O H^{\oplus} E t O H - -- \to C H_{3} - O H + B r^{⊖} \dots (i) C H_{3} - B r + O H^{\oplus} D M S O - --- \to C H_{3} - O H + B r^{⊖} \dots (i i)

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