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How do you find the number of hydrogen bonds between molecules?

  1. Feb 6, 2012 #1
    Hey, I'm wondering how you figure out the number of hydrogen bonds acting between molecules. I know each water molecule supposedly makes 4 hydrogen bonds with other water molecules through my reading, but I want to know how many for isopropyl alcohol, which has only one OH group. I know its less than water based on the properties of the two, but thats it. I think it may be either 1 or 3 but im not sure how to figure this out. Any help would be appreciated.
     
  2. jcsd
  3. Feb 6, 2012 #2
    If it were three, what hydrogens on isopropyl alcohol would be involved in hydrogen bonding?
     
  4. Feb 6, 2012 #3
    Hydrongens in the OH group of other molecules would be used. You could have two H from other molecules bond to the O of the original molecule and then the H (of the original molecule) bonds to the O of another. If that is allowed
     
  5. Feb 7, 2012 #4
    If its H-bonding with only one species present (IE neat EtOH) just look at the molecule and find the H-bond donor(s) and H-bond acceptor(s). It can get much more complicated if there are more than one species present (IE such as a solution or a mixture etc) because other effects, such as sterics and such, may play a role as to what H-bond with what

    So for EtOH, we have CH3CH2OH. One H-bond donor, but two lone pairs on the Oxygen can accept 2 H-bonds (from two other molecules of EtOH). So 1 molecule of EtOH can H-bond to three other EtOH molecules.
     
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