question_answer

\[{{S}_{N}}2\]mechanism is involved in the following substitution

A) \[C{{H}_{3}}-C{{H}_{2}}-Cl+O{{H}^{-}}\]

B)        \[C{{H}_{3}}-\underset{\begin{smallmatrix}  | \\  C{{H}_{3}} \end{smallmatrix}}{\overset{\begin{smallmatrix}  Cl \\  | \end{smallmatrix}}{\mathop{C}}}\,l-C{{H}_{3}}+O{{H}^{-}}\]

C)        \[C{{H}_{3}}-\overset{\begin{smallmatrix}  Cl \\  | \end{smallmatrix}}{\mathop{C}}\,H-C{{H}_{3}}+O{{H}^{-}}\]

D)        \[C{{H}_{3}}-C{{H}_{2}}-\underset{\begin{smallmatrix}  | \\  C{{H}_{3}} \end{smallmatrix}}{\overset{\begin{smallmatrix}  Cl \\  | \end{smallmatrix}}{\mathop{C}}}\,-C{{H}_{3}}+O{{H}^{-}}\]

Correct Answer: A

Solution :

\[{{S}_{N}}2\]mechanism means bimolecular nucleophilic substitution mechanism. In this, rate of reaction is determined by concentration of two molecules. It is characteristic of \[{{1}^{o}}\]alkyl halides. (a)\[\underset{{{1}^{o}}alkyl\,\,halide}{\mathop{C{{H}_{3}}-C{{H}_{2}}-Cl+O{{H}^{-}}}}\,\] (b)\[\underset{{{3}^{o}}alkyl\,\,halide}{\mathop{C{{H}_{3}}-\underset{\begin{smallmatrix}  | \\  C{{H}_{3}} \end{smallmatrix}}{\overset{\begin{smallmatrix}  Cl \\  | \end{smallmatrix}}{\mathop{C}}}\,-C{{H}_{3}}+OH}}\,\] (c)\[\underset{{{2}^{o}}alkyl\,\,halide}{\mathop{C{{H}_{3}}-\underset{\begin{smallmatrix}  | \\  Cl \end{smallmatrix}}{\mathop{C}}\,H-C{{H}_{3}}+O{{H}^{-}}}}\,\] (d)\[\underset{{{3}^{o}}\,\,alkyl\,\,halide}{\mathop{C{{H}_{3}}-C{{H}_{2}}-\underset{\begin{smallmatrix}  | \\  C{{H}_{3}} \end{smallmatrix}}{\overset{\begin{smallmatrix}  Cl \\  | \end{smallmatrix}}{\mathop{C}}}\,-C{{H}_{3}}+O{{H}^{-}}}}\,\]                                                 \[OH-\underset{\begin{smallmatrix}  | \\  H \end{smallmatrix}}{\overset{\begin{smallmatrix}  \downarrow  \\  C{{H}_{3}}  \\  | \end{smallmatrix}}{\mathop{C}}}\,-H+C{{l}^{-}}\]