Author
Home > Science > What is the Difference Between Iso and Sec in Organic Chemistry?

Guilherme Mazui

•3 minutes to read

What is the Difference Between Iso and Sec in Organic Chemistry?

🆚 Go to Comparative Table 🆚

In organic chemistry, the prefixes "iso" and "sec" are used to indicate the position of a functional group in a hydrocarbon chain. The difference between the two prefixes lies in the carbon atom to which the functional group is bonded.

  1. Iso: The prefix "iso" is used when the hydrocarbon has at most six carbon atoms in a chain and one carbon is present on the second last carbon atom of the chain. It is also used when all carbons except one form a continuous chain, and the functional group is bonded to the end of the chain. For example, iso-butyl has the structure CH3-CH-CH3.
  2. Sec: The prefix "sec" is used when the functional group is bonded to a secondary carbon atom, meaning that the carbon atom is attached to two other carbons. It is not used when the carbon chain is shorter than four. For example, sec-butyl has the structure CH3-C(CH3)3.

In summary:

  • Use "iso" when the functional group is bonded to the end of a continuous chain of carbon atoms or to the second last carbon atom in a chain with at most six carbons.
  • Use "sec" when the functional group is bonded to a secondary carbon atom, meaning the carbon atom is attached to two other carbons.
On this page
  • What is the Difference Between Iso and Sec in Organic Chemistry?
  • Comparative Table: Iso vs Sec in Organic Chemistry

    • Comparative Table: Iso vs Sec in Organic Chemistry

    The prefixes "iso" and "sec" in organic chemistry are used to indicate the position and attachment of substituents in branched alkanes. Here is a comparison table of the difference between "iso" and "sec" in organic chemistry:

    Prefix Meaning Attachment Example IUPAC Name
    iso New Latin for "equal" or "rotated" Substituent is attached to a primary carbon atom n-pentane, iso-propanol pentane, 1-propanol
    sec Secondary Substituent is attached to a secondary carbon atom sec-butanol 1-butanol
    • The prefix "iso" is used when all carbons except one form a continuous chain, and the substituent is attached to a primary carbon atom.
    • The prefix "sec" stands for "secondary" and is used when the substituent is attached to a secondary carbon atom, which is a carbon atom attached to two other carbons.

    Examples of the usage of these prefixes can be found in the structural names of alkanes with substituents:

    • isobutane (same as 2-methylpropane)
    • sec-butanol (same as 1-butanol)

    These prefixes help chemists identify and name complex branched alkanes with ease.

    Read more:

    Guilherme Mazui

    Guilherme Mazui is graduated in journalism from the Federal University of Minas Gerais (UFMG) and a master's degree in Communication from the University of São Paulo (USP). In addition, he has experience in advertising writing and has worked as a content editor in several companies.