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JEE Main & Advanced JEE Main Paper (Held On 25 April 2013)

  • question_answer
                    In nucleophilic substitution reaction, order of halogens as incoming (attacking) nucleophiles:                 \[{{\operatorname{I}}^{-}}>{{\operatorname{Br}}^{-}}>{{\operatorname{CI}}^{-}}\]                 The order of halogens as departing nucleophile should be :     JEE Main Online Paper ( Held On 25  April 2013 )

    A)                 \[B{{r}^{-}}>{{I}^{-}}>C{{l}^{-}}\]              

    B)                                        \[{{I}^{-}}>B{{r}^{-}}>C{{l}^{-}}\]

    C)                                        \[C{{l}^{-}}>B{{r}^{-}}>{{I}^{-}}\]              

    D)                                        \[C{{l}^{-}}>{{I}^{-}}>B{{r}^{-}}\]

    Correct Answer: B

    Solution :

                    Since the leaving group breaks away as a base, it is easier to displace weaker bases as compared to stronger bases. Thus less basic the substituent, the more easily it is displaced. Since the basic strength of the given groups is in order. \[{{I}^{-}}<B{{r}^{-}}<C{{l}^{-}}\] Thus the order of halogen leaving groups is \[{{I}^{-}}>B{{r}^{-}}>C{{l}^{-}}\]


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