$i$ $. CH_3CO_2H$
$II.$ $ MeOCH_2CO_2H$
$III.$ $CF_3CO_2H$
$IV.$
$1.\,\,\,\begin{array}{*{20}{c}} {C{H_3} - C - {O^ - }} \\ {\,\,\,||} \\ {\,\,\,O} \end{array}$ $2.\,\,CH_3O^-$ $3.\,\,CN^-$