Understanding the Context

What is CHCl₃?

CHCl₃, or chloroform, is an organochlorine compound with one carbon atom (C) bonded to one hydrogen atom (H), three chlorine atoms (Cl), and one lone pair of electrons. Its molecular formula is CCl₄ with a hydrogen replacing one chlorine—making CHCl₃ a monochlorinated derivative of chloroform. Though often confused with chloroform (CHCl₃), in certain reaction contexts, CHCl₃ refers to a reactive intermediate or hydrated form, influencing its Lewis structure and bonding description.

Lewis Structure Basics

Key Insights

Before diving into CHCl₃’s structure, a quick refresher on Lewis structures:
Lewis structures represent valence electrons around atoms to show bonding and lone pairs. They follow the octet rule, illustrating covalent bonds via shared electrons, and include lone pairs to depict non-bonding electron pairs.

Steps to Determine the CHCl₃ Lewis Structure

Step 1: Count Total Valence Electrons

• Carbon: 4 valence electrons
  
• Hydrogen: 1 × 2 = 2 electrons
  
• Each chlorine: 7 × 3 = 21 electrons
  
• Total = 4 + 2 + 21 = 27 electrons

Step 2: Draw a Skeletal Structure

• Central atom: Carbon (less electronegative)
  
• Attach atoms: one H and three Cls (H is terminal)
  
• Place single bonds: C–H, C–Cl (three times)

Final Thoughts

Step 3: Distribute Remaining Electrons

• Use 6 electrons for initial single bonds (3 bonds × 2 electrons each = 6)
  
• Remaining electrons = 27 – 6 = 21 electrons left

Step 4: Fill Lone Pairs

• Hydrogen already bonded, so assign 0 electrons
  
• Carbon has 4 – 1 (bonded H) = 3 valence electrons left → needs 3 more → one lone pair
  
• Each Cl has 7 – 1 = 6 electrons → 3 lone pairs per Cl
  
• Distribute remaining electrons:
  
  • Carbon lone pair: 2 electrons
    
  • Cl: 3 atoms × 6 = 18 electrons
    
  • Total so far: 2 + 18 = 20 → 1 electron void
    
  • Distribute one unpaired electron on one Cl to satisfy octet — forming a dipolar (polar) structure

CHCl₃ Lewis Structure Final Structure

• Central atom: Carbon
  
• Bonding:
  
  • One single bond (C–H)
    
  • Three single bonds (C–Cl)
    
• Lone pairs:
  
  • Carbon has one lone pair (two electrons)
    
  • Each chlorine has three lone pairs (6 electrons), contributing to polarity

Clː
|
H–C←Clː
|
Clː