Is CH3(CH2)8NH2 polar or nonpolar and why
The Correct Answer and Explanation is:
The molecule CH3(CH2)8NH2, known as octylamine, is polar. Here’s why:
- Structure and Functional Group: The molecule consists of a long alkyl chain (C8H17) and an amine group (NH2) at the end. The amine group has a nitrogen atom, which is highly electronegative and creates a partial negative charge on the nitrogen and a partial positive charge on the attached hydrogen atoms. This introduces a dipole moment in the molecule.
- Polarity of the Amine Group: The nitrogen atom in the amine group is more electronegative than carbon and hydrogen, which means it attracts electrons towards itself. This causes the nitrogen to develop a partial negative charge (δ−), while the hydrogen atoms connected to it develop partial positive charges (δ+). This gives the NH2 group a net dipole moment.
- Effect of the Alkyl Chain: The long alkyl chain (C8H17) is nonpolar because carbon-hydrogen bonds are not significantly polar due to the similar electronegativity of carbon and hydrogen. The chain is hydrophobic (water-repelling) and does not contribute to the overall dipole moment. However, the presence of the amine group at the end still makes the molecule polar.
- Resulting Dipole Moment: Because of the presence of the polar NH2 group at one end of the molecule, octylamine has an overall dipole moment. While the long alkyl chain tends to decrease the molecule’s polarity, the polar amine group dominates, making the molecule overall polar.
In summary, CH3(CH2)8NH2 is polar due to the presence of the polar NH2 group at one end, which creates a significant dipole moment, even though the long nonpolar alkyl chain reduces the overall polarity to some extent.
