Learn about Organic Chemistry 4, in this comprehensive video by bannanaiscool.
Read the full transcript »
Rob Lederer: The fun part comes in organic chemistry when you get apply with the models again. So, if your teacher doesn't have these you say, hey man, go and order some stickies and ballies. I want to play with some stickies and ballies man. Because this is the fun stuff right here. So, what's that? One carbon; carbons in black, right? The four hydrogens and that's going to be nothing, right there, yeah. And so, ethane - well, there is ethane right there and ethane is going to be -- now look, if you put the hydrogens right next to each other, since they don't bond with each other but they will repel each other with those two protons there are in nucleus, you kind of turn that a little bit and that's a preferable way of being able to show this molecule. So, ethane, two carbons, right? C2H6 right there that's a nice look. Now, what's the shape again around the methane molecule? Remember the bonding unit, that's going to be a tetrahedral with 109.5 degree bond angles between the hydrogen there and there and with the carbon in the centre, right? So, what's this shape right here? Look, don't freak out about it. Because really there is a tetrahedral around that carbon right there, if I hold those hydrogens there. Can you see that right there? Can you see that right there, there is a tetrahedral around this carbon here, but then there is a tetrahedral around this carbon here. So it's two tetrahedrals, so, you come by tetrahedral or d tetrahedral or something, don't worry about it. It's just two tetrahedrals that make up ethane. Now, what's that going to be? Yeah, that's right? One, two, three that's propane right there, right? Now, it's an ethyl group that is ready to attach as a branch on to something else. How clever is that. And I wanted to make sure that you remember this too. How about boiling points? Remember, that when two methane molecules come together to form a liquid or a solid, that can happen, of course because these gaseous molecules -- and by the way methane is a gas normally, of course, at room temperature, you have to cool it about negative 184 or so degree celsius to get it into a liquid. You can get these molecules to bond intermolecularly, right? And that's going to be because the protons of this molecule attract electrons here and vice versa that's called London Dispersion Force Bonding and because these molecules are non-polar, all the equivalent 109.53 bond angles, if I'm right; that means that this is going to be a substance that, since its non-polar and non-polar bonds through LDF. So, they can come together to form liquids and solids and we know that more protons and electrons we have in a molecule that means that we are going to have stronger LDF force, which means that when two ethane molecules bond together to form a liquid or a solid, they are going to form a stronger bond and subsequently, they are going to have a higher boiling point and a higher melting point. When you get the propane like propane has a boiling point around - well, let's see it's around in the minus 40's or so, but methane is around negative like I said 184. So, if you had a temperature at about minus 70 degrees and you had propane and ethane in that environment, propane would be a liquid, but the methane would still be a gas until you cool it to negative 184. So, remember that you have to understand that as you increase the number of protons and electrons just making the molecules bigger really in terms of carbons, you are going to increase the boiling points and the melting points. When you start to add on oxygen later to as a part of an organic molecule, and then we start to make polar molecules, which are going to have either higher boiling points.
Copyright © 2005 - 2015 Healthline Networks, Inc. All rights reserved for Healthline.