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Homework Help: Acidity of lactic acid and propanoic acid

  1. Jun 19, 2012 #1
    1. The problem statement, all variables and given/known data

    i) Is lactic acid,CH3CH(OH)COOH a stronger or weaker acid than propanoic acid (CH3CH2COOH)

    ii) Another question is does ketone reacts with phosphorus pentachloride PCl5?

    2. Relevant equations

    3. The attempt at a solution

    (i) I guess lactic acid is a stronger acid because the oxygen atom on the hydroxyl group is very electronegative thus increases the polarity of the -OH bond on the carboxyl group, so H+ are more easily released. (Please correct me if i am wrong)

    (ii) I can't find any relevant information from my text book and even on google, but I encountered this type of question from my exercise book.. Can anyone guide me?
  2. jcsd
  3. Jun 19, 2012 #2
    Hi Michael!

    For (i) you are correct that lactic acid is stronger. -OH in an alkyl chain acts as electron withdrawing due to -I effect.

    For (ii) you probably didn't google it well, as it is quite a standard reaction in organic chemistry. :tongue2:

    Ketones react with phosphorus penta-chloride to give acid chlorides.

  4. Jun 19, 2012 #3


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    Close, but not quite. The product isn't called an acid chloride.
  5. Jun 19, 2012 #4
    Whoops, I meant alkyl chlorides, specifically geminal.
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