Just to clarify here, when I said that "If the reactant rotated plane-polarised light in a clockwise direction, the product would rotate plane-polarised light in an anti-clockwise direction (and vice versa)", this is a bit of an oversimplification! Inversion of the bonds does occur, but that doesn't necessarily mean that the direction that plane-polarised light is rotated will always change. It will happen often, but not always.
Great video, thanks for making it. I have a question: 1:30 - When the bond breaks, do the all two of the single bond's electrons go to the Chlorine) or does only one go to the Chlorine? In your example, the carbon atom is a carbocation as C+ and then you have Cl-. This would mean that Carbon is missing one electron and Chlorine has gained one extra electron. How is this possible if Carbon now has 6 electrons (3 bonds) but needs 7 (one more) to be deemed C+. Cl- would make sense because it started with a full 8 electrons and then gained one more from the 50/50 split.
Great question. This type of bond breaking (represented by a regular curly arrow as shown here) is called heterolytic fission. This is where both of the electrons in the covalent bond go to one of the atoms. My video on the basics of reaction mechanisms (ua-cam.com/video/R4MSYTnJb1c/v-deo.html) has a visual representation of both homolytic and heterolytic fission. Rather than counting up the electrons around the carbon, consider what happens when a covalent bond is formed. Let's look at HCl as an example. Hydrogen has one electron in its outer shell, and chlorine has 7. When they form a covalent bond, they are sharing a pair of electrons, to provide each atom with a full outer shell (2 for hydrogen, 8 for chlorine). However, neither atom becomes charged. This is because electrons aren't being fully exchanged (like during an redox reaction), they are being shared, halfway between the two atoms. This is the key point. The hydrogen has neither gained nor lost an electron, it's just sharing with chlorine, so it remains neutral. Vice versa for chlorine. When a carbon atom has four bonds around it, that doesn't mean it's gained 4 electrons (or it would have a 4- charge). It's sharing its electrons with other atoms, so it remains neutral. So, let's bring this back to your original question. Why does carbon only have a single positive charge? It's because it isn't really losing two electrons. The chlorine just stops sharing its electron, and the carbon is only losing its own electron that it was sharing with the chlorine. Hence, the carbon is left with a single positive charge, and the chlorine is left with a single negative charge. On top of all of that, there must always be a conservation of charge. Hopefully it's pretty clear that Cl- forms, so to balance the charge, C+ must also form. I hope this helps!
Hi everyone, I'm excited to announce that I now have posters available for the reaction schemes in this video: Aliphatic reactions: rdbl.co/47y5oAk Benzene reactions: rdbl.co/41W1qQM Phenol reactions: rdbl.co/3NZc8QE Perfect for learning organic chemistry (and supporting the channel at the same time!) 👨🔬
Just to clarify here, when I said that "If the reactant rotated plane-polarised light in a clockwise direction, the product would rotate plane-polarised light in an anti-clockwise direction (and vice versa)", this is a bit of an oversimplification!
Inversion of the bonds does occur, but that doesn't necessarily mean that the direction that plane-polarised light is rotated will always change. It will happen often, but not always.
Brilliantly explained, thanks Dom! I'll definitely be directing my students here whenever this topic comes up :)
Thanks Shirin, I'm glad you enjoyed!
Great video, thanks for making it. I have a question:
1:30 - When the bond breaks, do the all two of the single bond's electrons go to the Chlorine) or does only one go to the Chlorine?
In your example, the carbon atom is a carbocation as C+ and then you have Cl-. This would mean that Carbon is missing one electron and Chlorine has gained one extra electron. How is this possible if Carbon now has 6 electrons (3 bonds) but needs 7 (one more) to be deemed C+. Cl- would make sense because it started with a full 8 electrons and then gained one more from the 50/50 split.
Great question. This type of bond breaking (represented by a regular curly arrow as shown here) is called heterolytic fission. This is where both of the electrons in the covalent bond go to one of the atoms. My video on the basics of reaction mechanisms (ua-cam.com/video/R4MSYTnJb1c/v-deo.html) has a visual representation of both homolytic and heterolytic fission.
Rather than counting up the electrons around the carbon, consider what happens when a covalent bond is formed. Let's look at HCl as an example. Hydrogen has one electron in its outer shell, and chlorine has 7. When they form a covalent bond, they are sharing a pair of electrons, to provide each atom with a full outer shell (2 for hydrogen, 8 for chlorine). However, neither atom becomes charged. This is because electrons aren't being fully exchanged (like during an redox reaction), they are being shared, halfway between the two atoms. This is the key point. The hydrogen has neither gained nor lost an electron, it's just sharing with chlorine, so it remains neutral. Vice versa for chlorine.
When a carbon atom has four bonds around it, that doesn't mean it's gained 4 electrons (or it would have a 4- charge). It's sharing its electrons with other atoms, so it remains neutral.
So, let's bring this back to your original question. Why does carbon only have a single positive charge? It's because it isn't really losing two electrons. The chlorine just stops sharing its electron, and the carbon is only losing its own electron that it was sharing with the chlorine. Hence, the carbon is left with a single positive charge, and the chlorine is left with a single negative charge.
On top of all of that, there must always be a conservation of charge. Hopefully it's pretty clear that Cl- forms, so to balance the charge, C+ must also form.
I hope this helps!
this was a great video but I really wish you had talked about solvents in it as well
this is an amazing video thank you
Thank you sir, these videos are lifesaver
Hi everyone, I'm excited to announce that I now have posters available for the reaction schemes in this video:
Aliphatic reactions: rdbl.co/47y5oAk
Benzene reactions: rdbl.co/41W1qQM
Phenol reactions: rdbl.co/3NZc8QE
Perfect for learning organic chemistry (and supporting the channel at the same time!) 👨🔬
Circa 1870
Gentleman, how shall we make Chemsitry harder to understand ?
2:15 Sn1 = 2 steps... Sn2 = 1 step
BRILLIANT
Thank you!!