Bond Enthalpies

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Andy Liao 1B
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Joined: Thu Jul 13, 2017 3:00 am

Bond Enthalpies

Postby Andy Liao 1B » Sat Jan 13, 2018 10:45 pm

I was wondering if resonance in molecules affects bond enthalpies. If so, how does it affect bond enthalpies? Can someone please explain?

Vincent Tse 1K
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Re: Bond Enthalpies

Postby Vincent Tse 1K » Sun Jan 14, 2018 12:03 am

I mean, the general trend of bond enthalpy exists and resonance shouldn’t "affect" the listed enthalpy since that one is found experimentally (whatever you see in those tables).
I'm not sure if this is entirely true, but theoretically the enthalpies listed should be the MEAN bond enthalpy of each structure, since, ideally those values are found via repeating/confirming experiments.
Hope that answers it? I'm not entirely sure what you mean by "affect". I guess it would "affect" it, in the sense that resonance should have been factored in.

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Re: Bond Enthalpies

Postby 905022356 » Sun Jan 14, 2018 12:47 pm

Absolutely! If you have a molecule in which a double bond can exist in two different positions, the enthalpy of both bonds is affected by resonance. The bond enthalpy of each bond should be about 1.5 times the enthalpy of the single bond.

Vincent Kim 2I
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Re: Bond Enthalpies

Postby Vincent Kim 2I » Sun Jan 14, 2018 3:15 pm

Resonance shouldn't necessarily affect bond enthalpy, as you can still use the values given to you to determine what you are looking for.

For example a single bond between CO has bond enthalpy of 358 kj/mol, while a double bond between CO has bond enthalpy of 799 kj/mol. Either way, you're adding the two numbers together, resonance only affecting which order you'd like to write it in. It's either 358 + 799, or 799 + 358, which is the same.

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