Hydrocarbon

Hey guys! In this new video, we're going to take a look at the concept of hydrocarbons. Hydrocarbons. The term of hydrocarbon refers to compounds that contain only carbons and hydrogens. Remember, hydro in Organic Chem does not mean water. Hydro actually refers two hydrogens. We're going to say these compounds may possess single, double or triple bonds. We’re going to say carbons are tetravalent. Remember, I've dropped this word numerous times. Carbon is tetravalent, meaning that when they aren’t neutral, they must make four bonds.
When carbon is neutral, it has two make four bonds any way that it can. There are rare exceptions where you're going to see a neutral carbon not making four bonds. Again, those rare exceptions, you'll see them more so in organic chemistry. When you first take Organic 1, you’ll hear about structures called carbines. Carbines are an exception to this. But don't worry, you typically don't learn about carbines until about two thirds of the way into Organic 1.
Here, alkanes anes, they have nothing but single bonds between their carbons and hydrogens. An alkene has at least one carbon double bonded to another carbon. Alkyne has at least one carbon triple bonded to another carbon. Then benzene is this special ring here that we have. All of these represent different types of hydrocarbons. They only have carbons and hydrogens in them.
Here knowing that is key to understanding how best to name them, what kind of reactions they undergo, a lot of different things. It all starts with being able to identify the different types of hydrocarbons that we have. So guys, once we've known these four different types, we can then move on to alkane prefixes. Make sure you come back and take a look at the next video where I talk about alkane prefixes.

Alright guys! Let's take a look at the alkane prefixes now. Here, alkane prefixes. The name of alkanes is based on the number of carbons in the compound. These alkane prefixes that go in the front must be memorized in order to name more complex structures later on in the chapter. We're going to be dealing with alkanes first, then move on to alkenes and then alkynes. Then we’re going to be incorporating things called functional groups, other things that look very different from them. They're all based initially on
memorizing these prefix names.
We're going to stay here if you have one carbon in you, your prefix name is meth. If you have six, then it's hex. If you have two carbons, then it’s eth. Seven carbons is hept. Three carbons is prop. Eight is oct. Four is but. Nine is non. Five is pent. Then ten is dec. If you have a three-carbon chain made up of only single bonds, you have an alkane, ane. So the name of the alkane will be propane. We use the prefix name and then alkanes end with ane, that's why it's called propane.
We're going to see how exactly do we use these prefixes to name alkanes and then more complicated types of organic molecules. We looked at this. We're going to move on to the next section. Make sure you come back and take a look at the next video and see how else this builds on top of what we learned so far.

Alright guys! So let's take a look at alkanes. Here we’re going to say alkanes are hydrocarbons that contain only single bonds, so there's only single bonds between the carbons and the hydrogens. They are sometimes referred simply as saturated hydrocarbons. Saturated means that every single carbon has as many hydrogens as possible on it. Since all of the carbons are connected to four groups, they all have an sp3-hybridization. Remember, if you’re sp3-hybridized you're connected to four different things whether they’d be elements or lone pairs. If you don't quite remember hybridization, make sure you go back and take a look at my other chapter videos where we talked about hybridization and how it relates to Lewis dot structures.
This is important. Alkanes have a generic formula. Their genetic formula is CnH2n+2, where n is the number of carbons. Here, remember we said on the last page that the alkane prefix when you have two
carbons is eth. Because this is only single bonds between the carbons and hydrogens, it's an alkane, -ane. That's why the ending is -ane. If we use this formula here, ethane has two carbons in it, so n is 2. If you work it out, it’s C2H6. That’s ethane’s formula.
Here if you have three carbons, we said that your prefix name was prop and it’s single bonds so it’s an alkane that's why the ending is ane. Then if we use that formula, it’s be C3 H 2 times 3 plus 2. Propane's formula is C3H8. We can use this formula to determine, do we have an alkane or not? Do we have an alkene or an alkyne?
Now that we've seen the basics in terms of this, we can take a look at what's going on in terms of figuring out the formula of a compound that's made up of only single bonds and eight carbons. I want you guys to attempt to name this example here. Come back and see how I answer it. Compare your answer to my answer.

Alright guys! Let's take a look at the alkene aspect now of hydrocarbons. Here, alkenes are hydrocarbons that contain at least one double bond. Once you start adding double bonds, which are pi bonds, you become unsaturated. Unsaturated just refers to the carbon is not having the maximum amount
of hydrogens possible. Here the double bonded carbons are connected to three electron groups, so those double bonded carbons have an sp2 hybridization.
Now here what we need to realize is if we take a look at ethene, ethane was those two carbons each one connected to three hydrogens. Notice the difference between them. In the alkane version, both carbons have three hydrogens. But once we create that double bond, what happens? We lose two hydrogens as a result. Why? Because here, those carbons can't be allowed to continue having three hydrogens each because then if we take a look at this carbon, it’s making one, two, three, four, five bonds. Carbon cannot make more than four bonds.
The trade-off is this. If you laid down an extra bond, you have to give up a hydrogen. Since we're laying down an extra bond between these two carbons, they each have to give up one hydrogen. Here, same thing here. It should have had an H here. Actually, it shouldn't have this H here at all. Make sure you do a correction of this. There shouldn't be an H there at all because that carbon is making five bonds. Remove that H there. I'll make sure to correct that on the PDF guys. But make sure that you realize right now that that carbon should not have two hydrogens on it. It should only have one.
Let's think about this. We're going to say here that the formula for an alkane is CnH2n+2. But when we put down a double bond, we lose two hydrogens. What would the formula of an alkene be? We lose two Hs so that two wouldn't be there anymore. The generic formula for an alkene with only one double bond would be CnH2n. Again, this is the generic formula for an alkene with only one double bond. But it also represents the formula for a cycloalkane. Because here if we think about it, this cycloalkane if we look has six carbons in it.
Remember every end, every corner is a carbon, each one we see making two bonds. Each carbon has two hydrogens we don't see. The formula of this thing would be C6H12. It has the same exact formula as an alkene, a compound with only one double bond. Why? Because the alkane form should have been C6 H 2 times 6 plus 2, so that would have been C6H14. What's the difference? We lost two hydrogens in order to make a ring. When you make a double bond, you have to give up two hydrogens. When you make a ring, you have to give up two hydrogens that's why they have similar formulas.
Here, this is just the basics in terms of identifying the formulas for an alkene and a cycloalkane. When you move on to Organic and I'm saying that a lot, you’re going to get more and more complex types of molecules. We’ll see a few today but just realize they get more and more complex. Now that we've seen this, let's see if you guys can try to answer this question here. I just need the formula and the simplest possible name of a hydrocarbon that contains one double bond and six carbons. Attempt this on your own and then come back and see how I best approach it. 

Hey guys! Let's take a look at the alkyne section now of hydrocarbons. We say alkynes are hydrocarbons that contain at least one triple bond. They are sometimes referred simply as unsaturated hydrocarbons just like the alkenes. The triple bonded carbons are connected to two electron groups, so either lone pairs are surrounding elements. Therefore, their hybridizations are sp3-hybridized. Here we're not laying down one pi bond. We're laying down two pi bonds to make a triple bond.
Remember, every time we put down an extra bond, we have to give up two hydrogens in the process. If we're putting down two bonds now, two extra bonds, that means that we're losing a total of four hydrogens because here, ethane originally had three hydrogens on each carbon. Now we have a triple bond there, so each carbon only gets one H. We keep minusing two every time we add an extra bond. For an alkyne with one triple bond, the generic formula would be H2n-2.
Notice two carbons is eth again for the prefix and because we have a triple bond, the ending is yne. This would be ethyne. Here, three carbons, the prefix would be prop because it ends with yne, that's because we have a triple bond so it's propyne. The name sounds a little bit funny, I know but this is how we would name them.
Now that we've seen this, let's see if you guys can attempt to do this question here. Now we're looking for basically a hydrocarbon, its generic name, nothing specific. It has one triple bond and nine carbons. Apply what we've learned so far and try to answer this question here. Come back. Click on the next video and see how I best answered that question.

Hey guys! Let’s look at this last section dealing with the fourth type of hydrocarbon – aromatic hydrocarbons. Here we're going to say aromatic compounds have a benzene ring in common. That's their major feature. Remember, a benzene ring is C6H6 because remember, every corner and edge is a carbon which I've displayed here. What we need to realize here is that you can draw it a bunch of different ways. We're going to say here maybe the double bond is here, here and here.
We're going to say that these double bonds overlap or they're alternating actually. Alternating will be a more correct term for them. These double bonds alternate. They go double bond, single bond, double bond. We're going to say that alternating double and single bonds they actually have a name in organic. It's called conjugation. Here's the thing about conjugation. If you can draw them alternating, that means you can draw them in different ways. We could draw the double bonds in that orientation or maybe the double bonds go this way. Both are possible structures. Because we are just moving around double
bonds or moving around electrons, we’re going to say these two initial drawings represent the resonance structures of benzene.
Here's the thing. Resonance structures are imaginary. They're not real. The real structure is called the resonance hybrid. It is basically a composite of both of these structures on top of each other. Basically think of it as they both have blueprints to the inside of a building. One alone doesn't have all the information you need. What happens here is you take one blueprint and you put the other one on top
and the composite is them lining up everything on top of each other and then you’ll get the complete picture of the building itself. That complete picture represents my resonance hybrid.
Here's the thing. Anywhere a double bond has been will get a dotted line. There was a double bond here, so this is going to get a dotted line. There was a double bond here so this is going to get a dotted line. Double bond here so it's going to get a dotted line. Basically anywhere a double bond has been is going to get a dotted line. That represents my resonance hybrid.
You may eventually see benzene written like this, not like those two resonance structures but instead you'll see a circle. That circle represents the resonance hybrid. Again, why is it a circle? Because the double bonds have been everywhere inside of that compound based on those two resonance structures. We just used a circle to show this. Me drawing these dotted lines where double bonds have been is basically me giving you the groundwork to draw this at the end. This also represents the resonance hybrid. They're both the same exact structure.
Here, benzenes can be found in everyday compounds from the gasoline that we drive, fossil fuels from oil rigs. There's a lot of places that you'll find benzene, even when we're breaking down fossil fuels and burning them. Some of the by-products are benzene. We're going to stay here even in some vital medications that people use every day, you can find benzene involved. Here for example, this molecule, huge molecule, I've highlighted in red the benzene ring. Right here is one benzene. Here's another benzene and here’s a third benzene. This is an incredibly important drug. This is Lipitor. For those people with high cholesterol, they use Lipitor to help control that. It controls your cholesterol. It controls the fat within your body. Everyday things from the fossil fuels that we use to drive machines around this world to even Lipitor that people get from the counter at the pharmacy. All of them have benzene involved.
Benzene is an incredibly versatile on compound. It's incredibly stable that's what you find it in a lot of different things. If you want to take Organic 2 eventually, you're going to realize that when you get to Organic 2, there are actually a few chapters entirely devoted to just benzene and compounds just like benzene, aromatic compounds. They're incredibly important in synthesis of a lot of other things so that's why so much detail is paid attention to them.
But for right now, just remember the basics in terms of it. It's C6H6. It has resonance structures but the resonance hybrid is the better example of what it looks like. Later on, we'll go over some of the reactions that benzenes commonly do but nothing too extravagant. Again, we're holding off a lot until you get to Organic 2.