A) \[{{C}_{6}}{{H}_{5}}CH({{C}_{6}}{{H}_{5}})Br\]
B) \[{{C}_{6}}{{H}_{5}}CH(C{{H}_{3}})Br\]
C) \[{{C}_{6}}{{H}_{5}}C(C{{H}_{3}})({{C}_{6}}{{H}_{5}})Br\]
D) \[{{C}_{6}}{{H}_{5}}C{{H}_{2}}Br\]
Correct Answer: C
Solution :
| [c] Key Idea \[{{S}_{N}}1\] reaction involves the formation of carbonation intermediate. More the stability of carbonation, more is the reactivity of alkyl/aryl halides towards \[{{S}_{N}}1\] reaction. |
| The intermediate carbonations formed by given halides are as: |
| \[{{C}_{6}}{{H}_{5}}CH({{C}_{6}}{{H}_{5}})Br\xrightarrow[{}]{{}}{{({{C}_{6}}{{H}_{5}})}_{2}}\overset{+}{\mathop{C}}\,H+B{{r}^{-}}\] |
| \[{{C}_{6}}{{H}_{5}}CH(C{{H}_{3}})Br\xrightarrow[{}]{{}}{{C}_{6}}{{H}_{5}}\overset{+}{\mathop{C}}\,H(C{{H}_{3}})+B{{r}^{-}}\]\[{{C}_{6}}{{H}_{5}}C(C{{H}_{3}})({{C}_{6}}{{H}_{5}})Br\xrightarrow[{}]{{}}\]\[{{({{C}_{6}}{{H}_{5}})}_{2}}\overset{+}{\mathop{C}}\,(C{{H}_{3}})+B{{r}^{-}}\] |
| \[{{C}_{6}}{{H}_{5}}C{{H}_{2}}Br\xrightarrow[{}]{{}}{{C}_{6}}{{H}_{5}}\overset{+}{\mathop{C}}\,{{H}_{2}}+B{{r}^{-}}\] |
| The order of stability of these carbocations is as\[{{({{C}_{6}}{{H}_{5}})}_{2}}\overset{+}{\mathop{C}}\,(C{{H}_{3}})>{{({{C}_{6}}{{H}_{5}})}_{2}}\overset{+}{\mathop{C}}\,H\]\[>{{C}_{6}}{{H}_{5}}\overset{+}{\mathop{C}}\,H(C{{H}_{3}})>{{C}_{6}}{{H}_{5}}\overset{+}{\mathop{C}}\,{{H}_{2}}\] |
| Thus, \[{{C}_{6}}{{H}_{5}}C(C{{H}_{3}})({{C}_{6}}{{H}_{5}})Br\] is most reactive towards \[{{S}_{N}}1\] reaction. |
You need to login to perform this action.
You will be redirected in
3 sec
