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Homework Help: 3-methylheptane draw the structure

  1. Oct 8, 2011 #1
    So I am given 3-methylheptane I know that it looks like this:

    And the methyl group is attached to CH

    It is heptane so I have 7 carbons and a total of 15 Hydrogens but I don't understand why it isn't 16 Hydrogens don't I use the formula
    If I don't use the formula then how do I determine the number of Hydrogens?

    Can someone please explain, I don't understand why one of it's Hydrogen is replaced with methyl, thanks!
  2. jcsd
  3. Oct 8, 2011 #2
    3-Methylheptane actually contains 8 carbons, not seven (Remember the naming, it is heptane (7 carbons), plus a methy group (on the 3rd carbon) is a -CH3 group). Thus, using your formula CnH2n+2, you should have C8H18, not C7H16 or C8H16. :)

    By the way, the structural skeleton form is: CH3-CH2-CH(CH3)-CH2-CH2-CH2-CH3
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