Question

Select the single best answer. Why is the boiling point of propanamide, CH3CH2CONH2, considerably higher than the boiling point of N,N−dimethylformamide, HCON(CH3)2 (213°C vs. 153°C), even though both compounds are isomeric amides? CH3CH2CONH2 has weaker intermolecular forces than HCON(CH3)2 hydrogen bonding is present in CH3CH2CONH2 but not in HCON(CH3)2 CH3CH2CONH2 is more branched than HCON(CH3)2 CH3CH2CONH2 has two methyl groups

Answer 1

The boiling point of propanamide is higher than that of N,N−dimethylformamide due to the presence of hydrogen bonding and increased branching in propanamide, resulting in stronger intermolecular forces.

Step-by-step explanation:

The boiling point of propanamide, CH3CH2CONH2, is considerably higher than the boiling point of N,N−dimethylformamide, HCON(CH3)2, even though both compounds are isomeric amides. The higher boiling point can be attributed to the presence of hydrogen bonding in propanamide, which is absent in N,N−dimethylformamide. Hydrogen bonding is a strong intermolecular force that requires more energy to break, leading to a higher boiling point. In addition, the branching of propanamide plays a role in increasing its boiling point, as increased branching results in a more compact molecule with stronger intermolecular interactions. Therefore, the correct answer is that CH3CH2CONH2 has weaker intermolecular forces than HCON(CH3)2.

Answer 2

Propanamide has higher boiling point due to higher hydrogen bonds interactions. N,N−dimethylformamide they do not have nitrogen bound hydrogens.

Step-by-step explanation:

The amides have abnormally high melting and boiling points. This phenomenon is due to the polar nature of the amide group and the formation of hydrogen bonds. Therefore, the combination of electrostatic forces and hydrogen bonds explains the intermolecular attractions so strong that they are observed in the amides. Note that tertiary amides do not contain nitrogen-bound hydrogens and, for this reason, do not form hydrogen bonds.

The following pictures show the polarities of the molecules, you can see that N,N-Dimethylmethanamide does not have any bond between nitrogen and hydrogens: