A) 1-bromo-2-butene under kinetically controlled conditions
B) 3-bromobutene under thermodynamically controlled conditions
C) 1-bromo-2-butene under thermodynamically controlled conditions
D) 3-bromobutene under kinetically controlled conditions
Correct Answer: C
Solution :
\[C{{H}_{2}}=CHCH=C{{H}_{2}}+HBr\xrightarrow{{}}\] \[\underset{1,\,\,2-addition\text{ }product}{\mathop{\underset{\begin{smallmatrix} | \\ Br \end{smallmatrix}}{\mathop{C{{H}_{3}}CHCH}}\,=C{{H}_{2}}+}}\,\underset{\begin{align} & \\ & \\ & \\ & 1,\text{ }4-addition\text{ }product \\ \end{align}}{\mathop{C{{H}_{3}}CH=CHC{{H}_{2}}Br}}\,\] Addition is through the formation of allylic carbocation. \[\underset{\begin{smallmatrix} (2{}^\circ \text{ }allylic) \\ (more\text{ }stable) \end{smallmatrix}}{\mathop{C{{H}_{2}}=CH\overset{\oplus }{\mathop{C}}\,HC{{H}_{3}}}}\,\overset{{}}{\longleftrightarrow}\underset{\begin{smallmatrix} (1{}^\circ \text{ }allylic) \\ (less\text{ }stable) \end{smallmatrix}}{\mathop{C{{H}_{3}}CH=CH\overset{\oplus }{\mathop{C}}\,}}\,{{H}_{2}}\] Under mild conditions (temperature\[\approx -80{}^\circ C\]) kinetic product is the 1, 2-addition product and under vigorous conditions (temperature\[\approx 40{}^\circ \]) thermodynamic product is the 1, 4-addition product. Thus, l-bromo-2-butene is the major product under given condition.
You need to login to perform this action.
You will be redirected in
3 sec
