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Homework Help: Which is strongest base?

  1. Sep 9, 2009 #1
    1. The problem statement, all variables and given/known data

    -OCH3, -OH, -NH2, and the fourth choice is an alkyle, ethyne with a neg charge. the picture shows a triple bond attacked to a hydrogen.

    2. Relevant equations

    3. The attempt at a solution

    I know that OH is a relatively common base and I thought it was strong, but I have no idea how it compares with the others. I know that alkyles are are less basic than alkenes and alkanes, but the oxygens throw me off a bit. I think that by having O in them it would suggest that their conj acid would be more acidic making them more basic. Is this correct at all? Is there an easy way to determine basicity?
  2. jcsd
  3. Sep 23, 2009 #2
    check the pKa of each conjugate acid. whichever has the highest pKa is the strongest base

    water = 15.7
    alcohols are between 16-18
    NH3 is ~35
    HCCH is ~25

    so NH2- is the strongest base
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