Question

Consider the molecule N,N-dimethylaniline, where the substituent −NMe₂ is present. Analyze the donor properties of −NMe₂ with respect to its electron distribution and bonding contributions. State the correctness of the following statement:

"The −NMe₂ group in N,N-dimethylaniline acts as a π-donor due to the presence of an unbound pair of electrons on the nitrogen atom, while simultaneously functioning as a sigma-donor through the influence of the two methyl groups."


a.Both the π-donor and sigma-donor roles of −NMe₂ in N,N-dimethylaniline are accurate.
b.The −NMe₂ group is exclusively a π-donor in N,N-dimethylaniline.
c.The −NMe₂ group solely acts as a sigma-donor in N,N-dimethylaniline.
d.The statement is inaccurate; the role of −NMe₂ in N,N-dimethylaniline differs from the described π-donor and sigma-donor characteristics.

Answer 1

The −NMe₂ group in N,N-dimethylaniline functions as both a π-donor, because of the unbound pair of electrons on the nitrogen, and as a sigma-donor, through its polar C-N bonds and interactions with the two methyl groups.

Step-by-step explanation:

The −NMe₂ group in N,N-dimethylaniline is indeed capable of exhibiting both π-donor and sigma-donor characteristics. This group contains an unbound pair of electrons on the nitrogen atom, which allows it to act as a π-donor. Due to nitrogen being more electronegative than the carbon to which it is bonded, the C-N bonds are polar, contributing to the sigma-donor properties.

The lone pair of electrons on the nitrogen can be donated to a proton, rendering the nitrogen positively charged and more reactive. Moreover, the two methyl groups attached to the nitrogen in the −NMe₂ group further contribute to its electron-donating capacity through the sigma bonds.