What is sec in organic chemistry?

The key difference between Iso and Sec in organic chemistry is that we use the term iso to name an organic compound containing all carbon atoms except one form a continuous chain whereas we use the term sec to identify a functional group that is bonded to a secondary carbon atom.

There are many prefixes in organic chemistry that we use to identify the groups present in compounds and to name organic molecules to distinguish them from each other. Furthermore, a better nomenclature system can name even a very complex molecule. Ex: IUPAC nomenclature is the best nomenclature system that gives each and every detail about the structure of a chemical compound.

1. Overview and Key Difference 2. What is Iso in Organic Chemistry 3. What is Sec in Organic Chemistry 4. Side by Side Comparison – Iso vs Sec in Organic Chemistry in Tabular Form 5. Summary

We use the term Iso to name an organic compound containing all carbon atoms except one form a continuous chain. This means, the term Iso refers to a carbon chain having one branch. Therefore, it is a prefix that we use to name organic compounds.

Most of the times, this one branch occurs at the end of the carbon chain, thus, we call this branch “terminal isopropyl group”. If there is a methyl group attached to the second carbon of a carbon chain, we use this prefix to name the molecule.

The term sec in organic chemistry refers to the attachment at a secondary carbon. This means we use this prefix when there is a functional group attached with a secondary carbon atom in a molecule. Sometimes we use “s” in the place of “sec”. However, both of these mean the same.

However, this prefix is useful for carbon chains having four or more than four carbon atoms. Unless otherwise, there cannot exist a secondary carbon. Therefore, its prefix is not applicable to a short chain carbon chain. Most importantly, a secondary carbon atom is a carbon atom in the middle of a carbon chain which has two carbon atoms bonded with it.

The term Iso in organic chemistry refers to an organic compound containing all carbon atoms except one form a continuous chain. The use of this prefix is to name a compound having a carbon chain containing one branch. The term Sec in organic chemistry refers to the attachment at a secondary carbon. The use of this prefix is to name a compound having a functional group attached to a secondary carbon atom in a molecule. This is the main difference between iso and sec in organic chemistyr.

The difference between Iso and Sec in organic chemistry is that we use the term Iso to name an organic compound containing all carbon atoms except one form a continuous chain whereas we use the term sec to identify a functional group bonded to a secondary carbon atom.

1. “Illustrated Glossary of Organic Chemistry – Common Names (n, Neo, Iso, Sec, Tert).” How to Use a Rotary Evaporator. Available here    2. Libretexts. “Nomenclature of Alkanes.” Chemistry LibreTexts, Libretexts, 8 Sept. 2017. Available here

1.’Butan-2-ol’By Kado6450 – Own work, (Public Domain) via Commons Wikimedia

The prefix "sec" or "s" is used when the functional group is bonded to a secondary carbon. This prefix is only useful for a four-carbon chain. It is not applicable with a shorter chain, and it is often ambiguous when the chain has five or more carbons.