Final answer:
The trans-dibromoethane is generally more stable than the cis-dibromoethane due to factors like reduced steric hindrance and lower dipole moment, not merely because of its symmetry. Symmetry does contribute to stability but is one of several factors including electronic effects and steric interactions.
Step-by-step explanation:
Stability of cis- and trans-Dibromoethane
It is a common question whether trans-dibromoethane is more stable than cis-dibromoethane due to its symmetrical nature. The stability of geometric isomers like cis and trans compounds often arises from several factors, including molecular symmetry, steric interactions, and electronic effects such as dipole moments. In general, trans isomers might be considered more stable due to less steric hindrance between groups attached to the carbon-carbon double bond.
For example, trans-1,2-dichloroethene is more stable than cis-1,2-dichloroethene because in the trans form, bulky substituents are on opposite sides, minimizing repulsive interactions. In the case of trans-dibromoethane, it is not solely the molecular weight distribution that contributes to stability, but also factors like reduced steric strain and lower dipole moment compared to its cis counterpart.
It is worth noting that while symmetry can contribute to stability, it is not the sole determinant. In cyclic compounds, such as cycloalkanes, the cis-trans isomerism plays a significant role in the physical properties of these isomers due to the restricted rotation around the carbon-carbon bond, which confirms them as distinct compounds, not just different forms of the same compound.