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Direction (1-5): The alkyi halides are extremely important reagents because they undergo a large variety of reactions that make them valuable in organic synthesis. This arises from the fact that the halide ion is a weak base and is readily displaced by stronger bases. This type of reaction is an example of nucleophilic substitution \[\left( {{S}_{N}} \right)\] since the attacking reagent is a nucleophilic reagent. This type of heterolytic reaction in solution can take place by two different mechanisms, unimolecular \[\left( {{S}_{N}}1 \right)\] or bimolecular \[\left( {{S}_{N}}2 \right)\].

\[{{S}_{N}}1\] reaction is a two step process and in the first step, R-X ionises to give carbocation (slow process). In the second step, the nucleophile attacks the carbocation from either side to form the product (fast process). \[{{S}_{N}}1\] reaction is favoured by heavy (bulky) groups on the carbon atom attached to halogens. \[{{S}_{N}}2\] reaction is a one stage process and two molecules simultaneously undergo covalency change in the rate determining step. In the transition state, the groups OH and X are collinear and on the opposite sides of attacked carbon. \[{{S}_{N}}2\] mechanism always lead to inversion of product. \[{{S}_{N}}2\]   reaction is favoured by small groups on the carbon atom attached to halogen. (I.L. Finar, Organic Chemistry Vol I. The fundamental principles Ch. 5, Sixth Edition).

Which among the following will not give \[{{S}_{N}}^{1}\] reaction?

A)  

B) \[{{\left( C{{H}_{3}} \right)}_{3}}C-Br\]

C) \[C{{H}_{3}}C{{H}_{2}}-I\]

D)