 So organic chemistry is the study of compounds that contain both carbon and hydrogen and the both pieces are very important here. For example CO2 carbon dioxide would be considered an inorganic compound because it does not contain hydrogen. Same thing for carbon monoxide that would be an inorganic compound or carbon tetrachloride is inorganic. So organic chemistry is a study of compounds that contain both carbon and hydrogen. If we look at a carbon atom and I've just drawn a rudimentary diagram of the carbon atom here and you can see that the carbon nucleus contains six protons and it contains six neutrons. So that gives us two electrons in the first shell and then four valence electrons. So the interesting thing about these four valence electrons is carbon will always form four covalent bonds and I'm just going to draw in some hydrogen atoms here. So each hydrogen of course has one proton in its nucleus and so each hydrogen will have one electron and you can see how carbon and hydrogen work out nicely together in that one carbon atom can form a covalent bond with four hydrogen atoms. So if we count electrons in the outer shell now we have one, two, three, four, five, six, seven, eight electrons in carbon's outer shell or is it sharing electrons with the hydrogen and then each hydrogen will have two electrons in its outer shell. So carbon will always form four covalent bonds. Now one thing that we can do to show some structural formulas for carbon is we can let a line represent a shared pair of electrons. So here's another way of representing CH4 which is methane. So one carbon with four hydrogens. This is actually the simplest of all organic compounds because it just contains carbon and hydrogen and of course we just have one carbon there. And it's similar to this diagram that we were looking at earlier. The only difference is instead of drawing all the electrons we're just letting a line represent a shared pair of electrons. So this is CH4 which is also known as methane. And methane is significant because it is the simplest of all organic compounds in that it just contains four hydrogens and one carbon. When we're studying organic chemistry we study families. I like the idea of families because like members of your family may share certain characteristics in common maybe you all have the same nose or the same ears or whatnot. Families of organic compounds share certain characteristics in common, certain chemical characteristics. The simplest organic compounds are called the hydrocarbons. And they're hydrocarbons because they contain only carbon and hydrogen. So there are no other atoms involved with hydrocarbons, only carbon and hydrogen. And there are three families of hydrocarbons. There are the alkanes, the alkenes, and the alkynes. All of these again just contain carbon and hydrogen. The alkanes have all single bonds between the carbons whereas the alkynes can have one or more double bonds between the carbons and the alkynes can have one or more triple bonds in the chain. So let's look at that some of the hydrocarbons and talk about their structure. Now I just want to write a few prefixes up here. Meth, these prefixes from geometry classes for example an octodon has eight sides or a decadon has ten sides. The pentadon has five sides. So these are prefixes that give us a clue as to how many numbers of carbons we have in this situation. So a compound that starts out with meth, like methane that we looked at just a second ago only has one carbon. F means two, probe means three. I always think about the propeller on the on the bow there. Butte means four, pent, five, hex, six, hept, seven, oct, eight, nine, nine, and dec, you know, pretend like decan. So let's bring up a program that will allow us to look at some of these simple hydrocarbons. And the first one is methane, which we looked at just a second ago. But you can see what methane looks like very nicely with this program. You can see that has what we call a tetrahedral shape with the way the hydrogens are positioned. So methane consists of one carbon and there are four hydrogens attached to it. And methane is the simplest of the organic compounds. Next let's look at ethane. So ethane has two carbons and you can see carbon one and carbon two. And then if you look as I spin it you can see that each carbon has three hydrogens attached to it. So this is ethane. It would be C2H6. We look at propane. Propane contains three carbons. So you can see one, two, three carbons. And then we counted, we would count up eight hydrogens. One, two, three, four, five, six, seven, eight. So as we add carbons our molecule gets longer. So here is butane with one, two, three, four carbons. You see we just have them all hooked together. And it's important to note that we can trace a line through our chain here. But there's another configuration for butane called isobutane that I want us to look at. Isobutane is interesting in that you see we can trace a line through three carbons. But then we have our fourth carbon attached to the middle carbon. So this is a situation in which we have different chemical structures, but we have the same molecular formula. And that's what isoburbs are all about. So if we go back and look at butane, you see with butane again we have four carbons in a line. But when we look at isobutane we have three in a line and then our fourth carbon is attached to the second carbon. Now this is important and we'll talk about some isomers later. For example sucrose and fructose are isomers of one another. Sucrose is table sugar and everyone knows how sweet table sugar is. Fructose is an isomer of sucrose but it tastes many times sweeter unless just due to the way the atoms are arranged. So we can go next to look at pentane. And this is just normal pentane and you can see that we have five carbons in a row and we can rotate it so we can see some different views of pentane but it's just essentially five carbons in a row. That's sort of looking at it straight down the line there. Hexane has six carbons in a row. One, two, three, four, five, six. And then we go to heptane with its seven carbons. One, two, three, four, five, six, seven. You can see all the hydrogens that are attached there. Octane of course will have eight and all we're doing is just making our our chain longer. Chain of carbons and hydrogens. Nine, we'll have nine carbons. One, two, three, four, five, six, seven, eight, nine. Again we just have a long chain and then we go to deckane which will have 10 carbons and you can see what deckane looks like here. Now the point of all this is just to demonstrate that families of organic compounds share certain characteristics in common and so the alkane is the simplest family of organic compounds that contain only carbon and hydrogen all single bonds between the carbons.