Is Benzil… A) Polar B) Slightly Polar C) Non-polar and explain why
The Correct Answer and Explanation is :
Benzil is a non-polar molecule. Despite containing polar bonds between carbon and oxygen atoms, the molecule’s symmetrical structure causes these dipole moments to cancel out, resulting in an overall non-polar character.
Structure and Symmetry:
Benzil consists of two benzene rings connected by a central carbonyl group (C=O). The carbonyl group is polar due to the electronegativity difference between carbon and oxygen. However, the molecule’s linear arrangement ensures that the dipole moments of the two carbonyl groups are aligned in opposite directions. This symmetry leads to the cancellation of the individual dipole moments, rendering the molecule non-polar.
Polarity of Benzil Isomers:
The polarity of benzil can vary depending on its isomeric form:
- Trans-Benzil: In this isomer, the two carbonyl groups are positioned on opposite sides of the central bond, maintaining the molecule’s symmetry. As a result, the dipole moments cancel out, making trans-benzil non-polar.
- Cis-Benzil: Here, the carbonyl groups are on the same side of the central bond, disrupting the symmetry. This arrangement prevents the cancellation of dipole moments, leading to a net dipole moment and making cis-benzil polar.
Implications for Solubility:
The non-polar nature of trans-benzil influences its solubility properties. It is more soluble in non-polar solvents like hexane, which can effectively dissolve non-polar compounds. In contrast, cis-benzil, being polar, would be more soluble in polar solvents such as ethanol or acetone.
In summary, the polarity of benzil depends on its isomeric form. Trans-benzil is non-polar due to its symmetrical structure, while cis-benzil is polar because of its asymmetry.