Question

Draw a Lewis structure for the \(N, N\) -dimethylformamide molecule. The skeletal structure is Various types of evidence lead to the conclusion that there is some double bond character to the \(\mathrm{C}-\mathrm{N}\) bond. Draw one or more resonance structures that support this observation.

Short answer

The Lewis structure for the N, N-dimethylformamide molecule is: H | H-C=N-C-H || | O H The resonance structures that support the double bond character of the C-N bond are: H | H-C=N-C-H || | O H H | H-C-N=C-H | \\ | O H These resonance structures indicate the delocalization of electrons in the C-N bond, and the actual structure of the molecule lies in between these two resonance structures.

Step-by-step solution

Determine the total number of valence electrons

First, we need to determine the total number of valence electrons in the molecule. The molecule consists of: - 1 Carbon (C) atom - 4 valence electrons - 1 Nitrogen (N) atom - 5 valence electrons - 3 Oxygen (O) atoms - (3x6) = 18 valence electrons - 6 Hydrogen (H) atoms - (6x1) = 6 valence electrons Total valence electrons = 4 + 5 + 18 + 6 = 33

Draw the Lewis structure

Based on the given skeletal structure - H | H-C-N-C-H | | O H Now, we will distribute the valence electrons to create a stable structure. We start by giving each atom an octet (except for hydrogen, which only requires two electrons). H | H-C=N-C-H || | O H We have achieved the stable structure with the correct number of valence electrons (33). The central carbon and nitrogen atoms have an octet, and the two terminal carbons have duets.

Draw resonance structures

Resonance structures show the delocalization of electrons in the molecule, which explains the double bond character of the C-N bond. We can show this by drawing a second resonance structure where the electrons are rearranged: H | H-C-N=C-H | \\ | O H These resonance structures represent the delocalization of electrons in the C-N bond. The actual structure of the N, N-dimethylformamide lies in between these two resonance structures, indicating that there is some double bond character to the C-N bond.