question_answer

Acid catalysed hydration of alkenes except ethene leads to the formation of     AIEEE  Solved  Paper-2005

A) pmixture of secondary and tertiary alcohols

B) mixture of primary and secondary alcohols

C) secondary or tertiary alcohol

D) primary alcohol

Correct Answer: C

Solution :

Write some acid catalysed hydration reactions of substituted alkene and check the results. \[C{{H}_{2}}=C{{H}_{2}}\xrightarrow{{{H}_{2}}O/{{H}^{+}}}C{{H}_{3}}C{{H}_{2}}OH\] \[C{{H}_{2}}-CH=C{{H}_{2}}\xrightarrow{{{H}_{2}}O/{{H}^{+}}}\underset{\begin{smallmatrix}  | \\  OH \end{smallmatrix}}{\mathop{C{{H}_{3}}CHC{{H}_{3}}}}\,\] (\[2{}^\circ \]alcohol) through \[2{}^\circ \] carbocation \[C{{H}_{3}}\overset{\oplus }{\mathop{CH}}\,C{{H}_{3}}\] \[C{{H}_{3}}-\underset{\begin{smallmatrix}  | \\  C{{H}_{3}} \end{smallmatrix}}{\mathop{C}}\,=C{{H}_{2}}\xrightarrow{{{H}_{2}}O/{{H}^{+}}}{{(C{{H}_{3}})}_{3}}COH\] (\[3{}^\circ \]alcohol) through\[3{}^\circ \]carbocation \[{{(C{{H}_{3}})}_{3}}\overset{\oplus }{\mathop{C}}\,\] \[C{{H}_{3}}-\overset{\begin{smallmatrix}  C{{H}_{3}} \\  | \end{smallmatrix}}{\mathop{CH}}\,-CH=C{{H}_{2}}\] \[\underset{{{3}^{o}}\,carbocation}{\mathop{C{{H}_{3}}-\underset{\oplus }{\overset{\begin{smallmatrix}  C{{H}_{3}} \\  | \end{smallmatrix}}{\mathop{C}}}\,-C{{H}_{2}}}}\,-C{{H}_{3}}\xrightarrow{{{H}_{2}}O}{{3}^{o}}alcohol\] Thus best alternate is (c).