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Radicals again - Formation energy

  1. Feb 13, 2018 #1
    I know my last question on radicals' interaction with luminol didn't get much attention, perhaps it was too specific.

    Please could I ask a last question, I understand that when radicals are formed via bond breaking this is called the bond-dissociation energy, but is there an energy associated with recombination?

    For example the energy required for the formation of the hydroperoxy radical from the hydrogen radical and oxygen? Do the oxygen bonds need to be broken in this process? Is it more energetically favourable to break the oxygen bonds than recombine into the hydroperoxy radical?

    Where would I find this information?

    Thanks again for any help.
  2. jcsd
  3. Feb 13, 2018 #2


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    Staff: Mentor

    Perhaps I am missing something about your question, but the answer looks painfully obvious: exactly the same energy, just with an opposite sign.
  4. Feb 14, 2018 #3
    I hadn't thought about it that way, thanks very much for the different persepective. I will look at the energy required to split the hydroperoxyl radical to give me the formation energy. I've been getting a little lost in radical chemistry and it's really not my area.

    Could you comment on my other question about the hydroperoxyl radical, do the O-O bonds remain intact in its formation? From the image...


    It certainly appears that way, but the oxygen no longer has double bonds. I am trying to determine if the energy required for breaking the O-O bonds would be less than the energy required to form the hydroperoxyl radical.

    Thanks again.
  5. Feb 14, 2018 #4
    edit It's ok think I have it now, from this list...


    H• + O2 = HO2

    Therefore to break HO2 we need to break the H-O bond (467 kJ/mol) and form an O-O bond (146 kJ/mol)
    To break an O2 bond it takes 495 kJ/mol

    Therefore, it requires more energy to form the hydroperoxyl radical than to break the O2 bonds, therefore hydroperoxyl radical formation will be more likely to happen for higher energy processes.
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