These are all the acyclic structura isomers for C3H6O2.
1-propene -1,1-diol, 1e-1-propene-1,2-diol, 1z-1-propene-1,2-diol1e-1-propene-1,3-diol, 1z-1-propene-1,3-diol2-propene-1,1-diol, 2-propene-1,2-diol
For C4H6,
1-butyne,
2-butyne,
1,2-butadiene,
1,3-butadiene
and cyclobutene