What are primary, secondary and tertiary carbons?

Posted on July 4th, 2012

Q&A from our students:

Question: What are primary, secondary and tertiary carbons? I know that sounds like a basic questions, but were just beginning to learn about alkanes and stuff and I don’t get it. Thanks.

Answer: It is a great questions and we’re am happy you asked because there are a lot of students who are confused about this subject. Let’s try to clear the air.

We use the terms primary, secondary, and tertiary to refer to the substitution level that a given carbon has in a molecule. In other words, these terms are used to describe how many other carbons a given carbon is attached to.

So to figure out the substitution level of any given carbon, follow these three easy steps:

Step #1: Pick a carbon

Step #2: Count how many carbons are directly attached to it. Other elements such as hydrogen, nitrogen, oxygen etc. don’t count.

Step #3: Give it a label:

  • Primary = a carbon attached to only ONE other carbon
  • Secondary  = a carbon attached to only TWO other carbons
  • Tertiary = a carbon attached to THREE other carbons

In the below example each carbon is color coded using the labels in step #3 above.

Go ahead give it a try!

 

 

OK- now bear in mind that hydrogens attached to a given carbon ALSO take on the labels as described in step #3 above.

So we can apply the same principle to the hydrogens:

  • Primary = a hydrogen on a carbon attached to only ONE other carbon
  • Secondary  = a hydrogen on a carbon attached to only TWO other carbons
  • Tertiary = a hydrogen on a carbon attached to THREE other carbons

 

You may submit a question to our experts by filling out the form at:

http://www.studyorgo.com/contact.php

You’re question may be answered in an upcoming blog posting!

Leave a Reply

You must be logged in to post a comment.