Question

How is ethanoic acid prepared from dry ice?

Answer 1

When the solution of methyl magnesium iodide (Grignard reagent) in dry ether is added to solid carbon dioxide (dry ice), it gives an adduct (magnesium salt of carboxylic acid), which on acid hydrolysis gives ethanoic acid or acetic acid.

Example:

\[\begin{array}{cc}
\ce{O=C=O +CH3-Mg-I->[Dry ether]CH3 -C-OMgI->[H3O+]CH3 -C-OH +Mg(OH)I}\\
\phantom{...}\text{Dry ice}\phantom{......}\text{Methyl}\phantom{.................}||\phantom{.....................}||\phantom{.................}\\
\phantom{..........}(\text{Solid carbon}\phantom{...}\text{Magnesium}\phantom{..............}\ce{O}\phantom{.......    ..............}\ce{O}\phantom{............................}\\
\text{dioxide})\phantom{.........}\text{iodide}\phantom{..............}\text{Adduct}\phantom{..............}\text{Acetic acid}\phantom{...........}\\
\phantom{...............................................}(\text{Ethanoic acid})
\end{array}\]