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Does KMnO4 really cleave double/triple bonds?

Discussion in 'MCAT Study Question Q&A' started by thebillsfan, 07.21.09.

  1. thebillsfan

    thebillsfan Unseasoned Veteran

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    I thought it only oxidized to alcohols...under what conditions can it cleave pi bonds?

    Also, what's the different between hot/acidic KMnO4 and cold/dilute KMnO4?
  2. G1SG2

    G1SG2

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    Hot/acidic KMnO4-cleaves double bonds to their carbonyl products, and even oxidizes the aldehydes to carboxylic acids.

    Cold/dilute KMnO4-makes a glycol/diol.
  3. thebillsfan

    thebillsfan Unseasoned Veteran

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    pookiez,

    so wouldnt it always oxidize to carboxylic acids, since cleavage of a double bond would always lead a terminal carbonyl (ie aldehyde)
  4. G1SG2

    G1SG2

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    No, cleavage of a double bond does not always lead to an aldehyde. Consider R2C=CRH. The KMnO4 cleaves the double bond to give R2C=O, a ketone and RCH=O, an aldehyde, which then gets oxidized to RCOOH, a carboxylic acid. Just picture yourself erasing the double bond and replacing it with two O's (that are not attached to each other, of course).
  5. loveoforganic

    loveoforganic -Account Deactivated-

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    For terminal alkynes, it oxidizes to a carboxylic acid and CO2. For an internal alkyne, it oxidizes to two carboxylic acids. ('it' being hot, acidic kmno4).
  6. G1SG2

    G1SG2

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    Yeah, also if it's neutral, then it'll oxidize an internal alkyne to a diketone.
  7. loveoforganic

    loveoforganic -Account Deactivated-

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    Cool, never knew that :p

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