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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: r12214001 on November 19, 2019, 01:03:03 PM

Title: Bond energy of Pi bond and sigma bond
Post by: r12214001 on November 19, 2019, 01:03:03 PM
It is well known that sigma bond is stronger than Pi bond. However in bond energy table that C=O is 745 KJ and C-O is 358 KJ. we can calculate the Pi bond energy is 745-358=387! The Pi bond(387KJ) is stronger than sigma bond(358KJ) ? How could this happen?
Title: Re: Bond energy of Pi bond and sigma bond
Post by: AWK on November 19, 2019, 03:24:52 PM
Quote from: r12214001 on November 19, 2019, 01:03:03 PM
It is well known that the sigma bond is stronger than the Pi bond.
It is well known that this simplification is not always true.

https://www.quora.com/What-is-the-ratio-between-a-pi-bond-and-a-sigma-bond-on-the-base-of-strength-and-why/answer/Daniel-James-Berger
Title: Re: Bond energy of Pi bond and sigma bond
Post by: Babcock_Hall on November 19, 2019, 04:25:57 PM
I found one table in which the value of 358 kJ/mole was given but notes that the values are averages.  I found a different table (see link below) which lists several C-O bonds, and one can see that they span a considerable range but all involve sp3-hybridized carbon atoms.
https://labs.chem.ucsb.edu/zakarian/armen/11---bonddissociationenergy.pdf