Final answer:
For the molecular formula C₄H₆, considering cyclic structures, there is only one unsaturated cyclic structure possible, which is cyclobutene, not accounting for possible stereoisomers.
Step-by-step explanation:
The question is concerned with finding the total number of unsaturated cyclic structures possible for a molecule with the molecular formula C₄H₆. An unsaturated hydrocarbon contains double or triple bonds. The simplest cyclic alkene we can construct from C₄H₆ would be cyclobutene, which would have one double bond within a four-carbon ring, satisfying the formula for an unsaturated compound (CnH2n). However, since double bonds can be located in different positions, there can be positional isomers. In the case of C₄H₆, there is only one cyclic alkene without considering stereochemistry.
Beyond alkenes, if we consider alkynes (compounds with triple bonds), the formula C4H6 is not consistent with a cyclic alkyne, as a triple bond would overly reduce the hydrogen count for a four-carbon ring.
Therefore, considering the molecular formula C₄H₆ for cyclic structures and not accounting for possible stereoisomers, the total number of unsaturated cyclic structures possible is one.