Thank you SO MUCH for this video! I'm an A-Level student reading Organic Chemistry by Clayden and this was a concept that was quite unclear to me before and to be honest, it's still not 100% clear but with time and watching this video a few times, I'm sure I can get it! This video explained the concept SO CLEARLY and for that, thank you!!!!
😎 A lot of practice on teaching these topics at my end - but also I figure your lecturers gave you a headstart. This is a topic that I’m very well aware of being taught really badly and usually in a very muddled way. That was my motivation for making this particular video, and several others on my channel(!)
Hi, I would be really glad if you made a video on orbital symmetry rules and orbital correlation diagrams. Like when a reaction is thermically allowed and when not
Hmm. That’s certainly something I’ll add to my to-do list but will have to have a think out how to pitch that into some interesting context. In the meantime I’d recommend Ian Fleming’s book on this topic which strips out some of the maths for the sake of focussing on the concepts.
what does suprafacial and antarafacial mean in terms of the orbitals? is it considered suprafacial if its the highest energy occupied MO of the pi system?
The terms very specifically don’t refer to any specific orbitals - they mean reacting on the same face of the molecule at each end, or reacting on opposite faces. So it doesn’t matter about the orbital phases or anything. The Woodward Hoffmann rules essentially consider all of the MOs for symmetry. Using phases and MOs is the now considered to be obsolete Frontier Molecular Orbital model (FMO), which is intuitively pretty but has been shown experimentally and computationally to be flawed
It’s a heavily grounded set of rules using Group Theory. Organic chemists formalise the results as I describe but they come from strict wavefunction symmetry on energy barriers between starting materials and products. I’m very tempted to make a video on these details. In the meantime if you’re interested Ian Fleming has published some pretty accessible books/ebooks on these topics
also what is the spontaneity of the reaction? it would seem difficult to combine two conjugated pi systems into an unconjugated product so i would assume a lot of heat to be involved
Yes often the classical Diels-Alder type things will need a lot of heat but largely for activation kinetic barrier. Forming the sigma bonds usually means the enthalpy change is negative and dominant
Though there are many examples of cycloadditions that can go closer to room temperature, particularly if they involve heteroatoms or are intramolecular.
Yes - that's the idea. It's a weird invasion of a numerical argument into organic chemistry. It all comes from orbital correlation diagrams to conserve the symmetry of the molecular orbitals through the reaction. Ian Fleming has published a reasonably accessible book from the organic chemist perspective if interested in looking further into the details.
Can I recommend the book by Ian Fleming on molecular orbitals in organic chemistry as a great introduction to pericyclic reactions and the Woodward-Hoffmann rules' origin. This video is pitched not right at the introduction of this topic for sure.
Thank you SO MUCH for this video! I'm an A-Level student reading Organic Chemistry by Clayden and this was a concept that was quite unclear to me before and to be honest, it's still not 100% clear but with time and watching this video a few times, I'm sure I can get it! This video explained the concept SO CLEARLY and for that, thank you!!!!
🙂 Cool - glad the video was helpful! It’s very much my ambition to make videos on topics that I do t think are traditionally explained well
why are you reading Clayden if youre only doing a level
How did you just explain to me in 10 minutes what my lecturer took 3 whole lectures to try and teach me
😎 A lot of practice on teaching these topics at my end - but also I figure your lecturers gave you a headstart. This is a topic that I’m very well aware of being taught really badly and usually in a very muddled way. That was my motivation for making this particular video, and several others on my channel(!)
The bigest humor to your teachers
Thank you so much for the video
:) Glad it was helpful
Thank you for your help
You’re welcome 🙂
Hi, I would be really glad if you made a video on orbital symmetry rules and orbital correlation diagrams. Like when a reaction is thermically allowed and when not
Hmm. That’s certainly something I’ll add to my to-do list but will have to have a think out how to pitch that into some interesting context. In the meantime I’d recommend Ian Fleming’s book on this topic which strips out some of the maths for the sake of focussing on the concepts.
@@CasualChemistry Do you maybe have the title of the book so I can check my university's library?
Molecular Orbitals and Organic Chemical Reactions
I’d hope they have a copy - it’s also available as an eBook do they might have a site licence
Thanks a lot, mate! Now I got it.
Cool 🙂 Glad the video was helpful
what does suprafacial and antarafacial mean in terms of the orbitals? is it considered suprafacial if its the highest energy occupied MO of the pi system?
The terms very specifically don’t refer to any specific orbitals - they mean reacting on the same face of the molecule at each end, or reacting on opposite faces.
So it doesn’t matter about the orbital phases or anything. The Woodward Hoffmann rules essentially consider all of the MOs for symmetry. Using phases and MOs is the now considered to be obsolete Frontier Molecular Orbital model (FMO), which is intuitively pretty but has been shown experimentally and computationally to be flawed
So can I see WH Rule as a model mathematical equivalent to what is actually at work here, used by scientists to simplify the thinking process?
It’s a heavily grounded set of rules using Group Theory. Organic chemists formalise the results as I describe but they come from strict wavefunction symmetry on energy barriers between starting materials and products.
I’m very tempted to make a video on these details. In the meantime if you’re interested Ian Fleming has published some pretty accessible books/ebooks on these topics
also what is the spontaneity of the reaction? it would seem difficult to combine two conjugated pi systems into an unconjugated product so i would assume a lot of heat to be involved
Yes often the classical Diels-Alder type things will need a lot of heat but largely for activation kinetic barrier. Forming the sigma bonds usually means the enthalpy change is negative and dominant
Though there are many examples of cycloadditions that can go closer to room temperature, particularly if they involve heteroatoms or are intramolecular.
at around 4:30 mins you talk about putting the pi numbers into (4q+2)s. why does the cyclopentadiene not count?
I understand now. as 4 isn't 2,6,10 it doesn't fir into (4q+2) so isn't considered
Yes - that's the idea. It's a weird invasion of a numerical argument into organic chemistry. It all comes from orbital correlation diagrams to conserve the symmetry of the molecular orbitals through the reaction. Ian Fleming has published a reasonably accessible book from the organic chemist perspective if interested in looking further into the details.
Thanks
No worries 🙂 glad you enjoyed the video
I don't get the explanation at all
Can I recommend the book by Ian Fleming on molecular orbitals in organic chemistry as a great introduction to pericyclic reactions and the Woodward-Hoffmann rules' origin. This video is pitched not right at the introduction of this topic for sure.
Thanks
:) Glad you found the video helpful