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

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:

For cyclohexane compounds drawn in a chair conformation:   -axial bonds are vertical  -equatorial bonds are parallel to two bonds within the ring.  thus, as i assume the chair conformation is drawn:   -the x group is in an axial position, as are the five other vertical bonds.  -three axial bonds are on the top face of the ring  -the other three axial bonds are on the bottom face  the position of the second substituent on each ring carbon is equatorial.  gauche groups must be on an adjacent carbon such as carbon 6 and carbon 2, and also gauche groups are rotated by 60 degrees relative to each other.  drawing the newman projections for c1–c2 and c1–c6 aids in visualizing the groups that are gauche to the y group on c1.  click this link and watch some academic videos that may you more understand the topic 

C. 1s22s22p63s23p43d104s24p5