Why do heteroatoms help determine the physical and chemical properties of a molecule?
a They forms more bonds to other atoms than carbon can.
b They possess nonbonding pairs of electrons and affect the molecule’s polarity.
c They possess stronger bonds with hydrogen atoms making the hydrogen atoms less acidic.
d They make the molecule lighter than it otherwise would be with carbon.
The answer to the question is (b) They possess nonbonding pairs of electrons and affect the molecule's polarity.
Heteroatoms, which are atoms other than carbon in a molecule, play a significant role in the physical and chemical properties of a molecule. This is primarily because heteroatoms introduce different electronegativities and valence electron configurations compared to carbon.
One of the key reasons heteroatoms affect the properties of a molecule is their ability to possess nonbonding pairs of electrons. These are lone pairs of electrons that are not involved in bonding with other atoms. The presence of nonbonding electron pairs can significantly influence the molecule's polarity.
In a molecule, if a heteroatom has one or more nonbonding electron pairs, it can create an uneven distribution of electrical charge, resulting in regions of partial positive and partial negative charges. This overall separation of charge gives rise to a polar molecule, which means it has both positive and negative poles. This polarity can affect various properties like solubility, boiling point, melting point, and polarity-dependent interactions such as hydrogen bonding.
Heteroatoms can also affect the acidity or basicity of a molecule. For example, by possessing stronger bonds with hydrogen atoms, heteroatoms can make the attached hydrogen atoms less acidic. This is observed in organic compounds where a heteroatom, such as oxygen or nitrogen, can stabilize the negative charge on an adjacent carbon atom, reducing its acidity.
Therefore, heteroatoms, through their nonbonding electron pairs and associated effects on polarity and acidity, contribute to determining the physical and chemical properties of a molecule.