How to Identity Carbon Multiplicity

Are you struggling with identifying whether a carbon is primary 1°, secondary 2°, tertiary 3°, or quaternary 4°? You are not alone. Here is how you do it with a very simple trick. But, first, how about some simple definitions.

• 1° Primary – one adjacent (attached) carbon
• 2° Secondary – two adjacent (attached) carbons
• 3° Tertiary - three adjacent (attached) carbons
• 4° Quaternary - four adjacent (attached) carbons

To identify them, follow these steps:

1. Draw a ring about the carbon you are interested in.
2. Count the lines (bonds) inside the circle
3. If the line all lead to carbons, then that’s your answer

For lines that are not attached to carbon:

  4. Subtract (ignore) lines not attached to carbon for a final answer