Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Name the following molecule (common name and IUPAC)?

  1. Sep 12, 2012 #1
    http://img43.imageshack.us/img43/2916/95953925.jpg [Broken]

    I understand molecule #1 is sec-pentylcyclohexane
    But how would you call molecule 2?

    Please give common and IUPAC names (no need for too much detailed explainations)
    Thank you.
     
    Last edited by a moderator: May 6, 2017
  2. jcsd
  3. Sep 12, 2012 #2

    jedishrfu

    Staff: Mentor

  4. Sep 12, 2012 #3
    any iso/sec/tert name for it?
     
  5. Sep 12, 2012 #4

    chemisttree

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    No you don't. Try again.
     
    Last edited by a moderator: May 6, 2017
  6. Sep 12, 2012 #5
    Why not?
    Here is sec-butylcyclohexane:
    cas7058-01-7.gif

    And another carbon to the chain simply makes it pentyl, am I wrong?
     
  7. Sep 12, 2012 #6

    chemisttree

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

  8. Sep 13, 2012 #7
    yes, the two systems are 2-pentylcyclohexane and 3-pentylcyclohexane.

    These are both common and IUPAC names.

    The sec- iso- tert- type names are confusing and only really useful for industrial compounds commonly known by these names or chains of 4 or fewer carbon atoms. For pentyl systems, the traditional nomenclature is even more confused by the intrusion of "amyl"

    "Common" or "industrial" names are not really worth knowing these days unless you are working with shipments of stuff. There are about 20 isomers of octane. n-octane is the straight chain isomer. There is no possible way you could know without looking it up or working with it that iso-octane is 2,2,4-trimethylpentane!
     
  9. Sep 13, 2012 #8
    I would need to know iso, sec and tert for my exam.. Some answers you should pick appear as iso\sec\tert rather than IUPAC formal names.. I wish it wasn't like that
     
  10. Sep 13, 2012 #9

    chemisttree

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    I think you'll find that where you are presented 'sec-' or 'tert-' substituted alkanes there will be only one obvious answer. Sec-butylcyclohexane is unambiguous since the cyclohexyl substitution at either secondary carbons results in a single product. That isn't the case with sec-pentylcyclohexane. Substitution at either the 2 or the 3 position is correct for that name so the ambiguity resulting from that nomenclature will result in misidentification or miscommunication and shouldn't be used.

    BTW, a typical test question reads, "The name sec-butyl alcohol defines a specific structure but the name sec-penty alcohol is ambiguous. Explain."

    So now you know.
     
  11. Sep 18, 2012 #10
    Tongue in cheek and only very marginally relevant to the OP question :-

    Another test question: "The name sec-butyl alcohol does not unambiguously define a single substance. Nor does the IUPAC designation 2-butanol. Explain why not, and how to rectify the nomenclature."
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Name the following molecule (common name and IUPAC)?
  1. IUPAC names (Replies: 17)

Loading...