question_answer

Write down the structure of the product of the following reactions. (i) \[C{{H}_{3}}-\underset{\begin{smallmatrix}  | \\  C{{H}_{3}} \end{smallmatrix}}{\overset{\begin{smallmatrix}  C{{H}_{3}} \\  | \end{smallmatrix}}{\mathop{C}}}\,-Br\,\xrightarrow[{{C}_{2}}{{H}_{5}}OH]{{{C}_{2}}{{H}_{5}}ONa}?\]   (ii) 3-Methyl-1-butene \[\xrightarrow{HBr}\]?

Answer:

                (i) \[3{}^\circ \]Alkyl halides on treatment with a strong base undergo dehydrohalogenation to form alkenes, i.e., (ii) Addition of \[{{H}^{+}}\] to 3-methyl-1-butene first gives \[2{}^\circ \] carbocation \[(I)\] which being less stable rearranges to the more stable \[3{}^\circ \] carbocation \[(II)\]. Nucleophilic attack by \[B{{r}^{-}}\] ion on this carbocation gives 2-bromo-2-methylbutane as the major product,