$\mathop {C{H_3} - \mathop C\limits^ \oplus H - C{H_3}}\limits_I $
$\mathop {C{H_3} - \mathop C\limits^ \oplus H - OC{H_3}}\limits_{II} $
$\mathop {C{H_3} - \mathop C\limits^ \oplus H - C{H_2} - OC{H_3}}\limits_{III} $
$(I)$ $CH_2 = CH - C \equiv CH$
$(II)$ $CH \equiv C - C\equiv CH$
$(III)$ $CH_3 - CH = CH_2$
$(IV) $ $CH_2 = CH - C = CH_2$