question_answer

Which of the following combinations can be used to synthesise ethanol?

A)  \[C{{H}_{3}}MgI\] and \[C{{H}_{3}}COC{{H}_{3}}\]

B)  \[C{{H}_{3}}MgI\] and \[{{C}_{2}}{{H}_{5}}OH\]

C)  \[C{{H}_{3}}MgI\] and \[CH{{H}_{3}}COO{{C}_{2}}{{H}_{5}}\]

D)  \[C{{H}_{3}}MgI\] and \[HCOO{{C}_{2}}{{H}_{5}}\]

Correct Answer: C

Solution :

When ethyl acetate is treated with excess \[C{{H}_{3}}MgI\], it gives t-butanol along with the elimination of ethanol \[C{{H}_{3}}-\overset{O}{\mathop{\overset{||}{\mathop{C}}\,}}\,-O{{C}_{2}}{{H}_{5}}+C{{H}_{3}}MgI\xrightarrow{{}}\] \[C{{H}_{3}}-\underset{C{{H}_{3}}}{\mathop{\underset{|}{\mathop{\overset{OMgI}{\mathop{\overset{|}{\mathop{C}}\,}}\,}}\,}}\,-O{{C}_{2}}{{H}_{5}}\xrightarrow[\begin{smallmatrix}  -{{C}_{2}}{{H}_{5}}OH \\  (ethanol) \end{smallmatrix}]{{{H}_{2}}O}\left[ C{{H}_{3}}-\underset{C{{H}_{3}}}{\mathop{\underset{|}{\mathop{\overset{OH}{\mathop{\overset{|}{\mathop{C}}\,}}\,}}\,}}\,-OH \right]\]   \[\xrightarrow{C{{H}_{3}}MgI}C{{H}_{3}}-\underset{C{{H}_{3}}}{\mathop{\underset{|}{\mathop{\overset{C{{H}_{3}}}{\mathop{\overset{|}{\mathop{C}}\,}}\,}}\,}}\,-OMgI\xrightarrow{{{H}_{2}}O}\underset{t-bu\tan ol}{\mathop{C{{H}_{3}}-\underset{C{{H}_{3}}}{\mathop{\underset{|}{\mathop{\overset{C{{H}_{3}}}{\mathop{\overset{|}{\mathop{C}}\,}}\,}}\,}}\,-OH}}\,\]