Draw the complete orbital diagram for formamide HCONH2. Clearly state the hybridization of each atom, clearly state the orbitals being drawn, and show the hybridization of each heteroatom.
The correct answer and explanation is :
Orbital Diagram and Hybridization of Formamide (HCONH₂)
Formamide (HCONH₂) has the molecular formula HCONH₂ and consists of the following atoms: carbon (C), oxygen (O), nitrogen (N), and hydrogen (H). To construct the complete orbital diagram, we must analyze the hybridization and bonding within the molecule.
Step 1: Hybridization of Each Atom
- Carbon (C):
- Carbon in formamide forms three sigma (σ) bonds: one with oxygen (O) and two with nitrogen (N) and hydrogen (H).
- It also forms one π-bond with oxygen due to the C=O bond.
- Carbon has sp² hybridization (one s orbital + two p orbitals → three sp² hybrid orbitals).
- The unhybridized p orbital is used to form the π bond in the C=O double bond.
- Oxygen (O):
- Oxygen forms one sigma bond (σ) with carbon and a π-bond using a p orbital.
- It also has two lone pairs.
- Oxygen is sp² hybridized: it uses three sp² orbitals for the lone pairs and the sigma bond, while one unhybridized p orbital participates in π-bonding.
- Nitrogen (N):
- Nitrogen forms two sigma bonds (one with carbon, one with hydrogen).
- It also has a lone pair of electrons.
- Due to resonance, nitrogen is sp² hybridized (rather than sp³). The lone pair occupies one of the sp² orbitals.
- Hydrogen (H):
- Each hydrogen forms a single sigma bond using 1s orbitals.
Step 2: Orbital Representation
- Sigma (σ) bonds:
- C=O sigma bond: sp² (C) – sp² (O)
- C-N sigma bond: sp² (C) – sp² (N)
- N-H sigma bonds: sp² (N) – 1s (H)
- C-H sigma bond: sp² (C) – 1s (H)
- Pi (π) bonds:
- C=O π bond: p (C) – p (O) (unhybridized orbitals).
- Nitrogen’s lone pair occupies an sp² orbital, allowing delocalization.
Step 3: Orbital Diagram Representation
The orbital diagram consists of:
- Sigma (σ) framework: Shows the overlap of sp² hybrid orbitals forming single bonds.
- Pi (π) framework: Shows the overlap of unhybridized p orbitals in the C=O bond.
- Lone Pairs: Represented in sp² hybrid orbitals on nitrogen and oxygen.
The resonance between C=O and C-N results in partial double bond character, stabilizing the molecule.