Basic Idea of Wedge–Dash Notation

Writing wedge–dash (3D) configuration is a key skill in stereochemistry (very important for JEE/NEET). Let’s make it simple and practical.

It shows how atoms are arranged in 3D space around a carbon atom.

3 types of bonds:

  1. Straight line (—)
    → Bond lies in the plane of the paper
  2. Solid wedge (▲)
    → Bond coming out toward you
  3. Dashed wedge (▱ / —)
    → Bond going away from you

How to Draw Wedge–Dash Structure (Step-by-step)

Step 1: Identify the central atom

Usually a chiral carbon (sp³ hybridised) with 4 different groups.

Step 2: Draw two bonds in plane

Use simple straight lines for 2 groups

Step 3: Add wedge and dash

  • One group → solid wedge (toward you)
  • One group → dashed wedge (away from you)

Important Rules

✔ Carbon must be tetrahedral (109.5°)
✔ Always show 3D orientation clearly
✔ You can rotate the molecule, but relative positions must stay same

Interconversion Tip (Fischer → Wedge-Dash)

  • Horizontal bonds in Fischer → come out (wedge)
  • Vertical bonds → go back (dash)

Common Mistakes

❌ Putting all bonds in plane
❌ Using wedge/dash randomly
❌ Changing configuration while rotating

Exam Trick (JEE/NEET)

If lowest priority group (4th) is on:

  • Dash (away) → read order normally
  • Wedge (toward) → reverse R/S result

Leave a comment