

$\mathop C\limits_{\mathop |\limits_{COOH} } {H_2}\, - \,\,\mathop {\mathop C\limits^{\mathop |\limits^{OH} } }\limits_{\mathop |\limits_{COOH} } \,\, - \,\,C{H_2}\,\, - \,\,\mathop C\limits_{\mathop {||}\limits_O } \,\, - \,\,OH$
$\mathop { - CH{{(C{H_3})}_2}}\limits_1 \,\,\,\,\,\,\,\,\,\,\,\mathop { - C{H_2}C{H_2}Br}\limits_2 \,\,\,\,\,\,\,\,\,\,\mathop { - C{H_2}Br}\limits_3 \,\,\,\,\,\,\,\,\,\,\mathop { - C{{(C{H_3})}_3}}\limits_4 $
$I = II = III = IV$