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Help needed with reaction equation

  1. Apr 18, 2008 #1
    Please can somone help me.

    I need to write an equation for the reaction between pentan 3 one and 2,4-dinitrophenylhydrazine.

    I am not very good with this area of chemistry so any help will be much appreciated.

    Ta
     
  2. jcsd
  3. Apr 18, 2008 #2
    Last edited: Apr 18, 2008
  4. Apr 18, 2008 #3

    chemisttree

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    The Wolff-Kishner reaction is the reduction that (typically) follows this reaction of a ketone with hydrazine (H2N2H2). I'm not sure it works on a DNP derivative, though. DNP derivatives are usually employed for melting point determinations.
     
  5. Apr 18, 2008 #4
    DNP-hydrazine (from the OP) is used to test exclusively for the presence of ketone carbonyls within a molecule via the general Wolff-Kishner reduction. This procedure is known as Brady's Test, which is positive upon formation of a yellow or red precipitate (see Analyst, 1926, 51, 77 - 78, DOI: 10.1039/AN9265100077)
     
    Last edited: Apr 18, 2008
  6. Apr 18, 2008 #5

    chemisttree

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    That's almost correct. Brady's test is specifically the formation of the DNP derivative itself (both ketones and aldehydes)... not it's further reduction to the alkane if only hydrazine itself were used (Wolff-Kishner Reduction).

    The Wolff-Kishner reduction is a specific reaction utilizing an aldehyde or ketone and hydrazine (NOT 2,4-DNP a different 'hydrazine') and a strong base to yield an alkane. Wolff-Kishner is NOT Brady's test. Some elements of the chemistry are similar, however.
     
  7. Apr 18, 2008 #6
    Indeed--I should have first looked this up on Wikipedia!
    http://en.wikipedia.org/wiki/2,4-Dinitrophenylhydrazine
    (even at best, the most convenient reference for this concept)

    --Accordingly, no reduction occurs but rather the precipitation of the DNP-derivative
    itself and yes, aldehydes as well as ketones are detected by Brady's test
     
    Last edited: Apr 18, 2008
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