Which of the following compounds are nonpolar

Which of the following compounds are nonpolar? 1) 3-methyl-2-hexanone 2) propanal 3) pentane 4) 2,3-dimethylhexane 5) 2-butanamine

The correct answer and explanation is:

The nonpolar compounds from the list are:

3. Pentane
4. 2,3-Dimethylhexane

Explanation:

Polarity of a compound depends largely on the presence of polar bonds (such as C=O, N-H, O-H) and the overall molecular geometry, which can either reinforce or cancel dipole moments.

1. 3-methyl-2-hexanone is a ketone. It contains a carbonyl group (C=O), which is highly polar because oxygen is much more electronegative than carbon. This polar group gives the molecule a significant dipole moment, making it polar.
2. Propanal is an aldehyde with a carbonyl group (C=O) at the end of the chain. Like ketones, aldehydes have a strong dipole due to the carbonyl group, so propanal is polar.
3. Pentane is a straight-chain alkane with only carbon and hydrogen atoms connected by nonpolar C–C and C–H bonds. Alkanes are generally nonpolar because the electronegativity difference between carbon and hydrogen is very small, and the molecule is symmetrical enough to have no net dipole moment.
4. 2,3-Dimethylhexane is a branched alkane, also consisting only of carbon and hydrogen atoms. Like pentane, it is nonpolar for the same reasons: mainly nonpolar bonds and no polar functional groups.
5. 2-Butanamine contains an amine group (-NH2), which has a nitrogen atom bonded to hydrogens. Nitrogen is more electronegative than carbon or hydrogen, creating a polar N-H bond. This makes 2-butanamine polar because of the amine group’s dipole.

In summary, compounds without strongly electronegative atoms bonded to carbon or hydrogen and without polar functional groups are generally nonpolar. This is true for pentane and 2,3-dimethylhexane, both alkanes, making them nonpolar compounds on the list.