Question

What structural feature of cycloalkanes makes cis, trans isomerism in them possible?

Short answer

Answer: The rigidity and restricted rotation of the cycloalkane's ring structure makes cis, trans isomerism possible, leading to different geometric arrangements of atoms or groups around the carbon atoms within the molecule.

Step-by-step solution

Define Isomerism and Cycloalkanes

Isomerism is a phenomenon where two or more compounds have the same molecular formula but different molecular arrangements. Cycloalkanes are saturated hydrocarbons containing a single-ring structure with multiple carbon atoms linked in a closed loop.

Explain Cis and Trans Isomerism

Cis and trans isomers are a type of geometric isomer in which the same groups are located on different sides of a double bond or a ring structure in the molecule. In cis isomers, the groups are present on the same side, while in trans isomers, the groups are present on opposite sides.

Investigate the Structural Features of Cycloalkanes that Allow for Cis, Trans Isomerism

Cycloalkanes have a rigid ring structure with restricted rotations around carbon-carbon single bonds due to their cyclical nature. This rigidity and restriction in rotation lead to different arrangements of atoms and groups around the carbon atoms, making cis, trans isomerism possible.

Explain Examples of Cis, Trans Isomerism in Cycloalkanes

An example of cis, trans isomerism in cycloalkanes is found in disubstituted cyclohexanes. In cyclohexanes, two hydrogen atoms can be replaced by functional groups. Since cyclohexane has a chair conformation, these groups can occupy the axial (up or down) or the equatorial (around the ring) positions. When both groups are in the equatorial positions on the same side of the ring, the molecule is considered a cis isomer. When the groups are in the equatorial positions on opposite sides of the ring, the molecule is regarded as a trans isomer. In conclusion, the structural feature of cycloalkanes that makes cis, trans isomerism possible is the rigidity and restricted rotation of their ring structure, which leads to different geometric arrangements of atoms or groups around the carbon atoms within the molecule.