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

Answer:

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

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: