So, in organic chemistry, we often talk about functional groups. Functional groups are groups of atoms that can be added to a hydrocarbon chain, for example. And so I've listed some of the major functional groups that students and biology might be interested in. One group is a hydroxyl group, and this is what alcohols are all about. So if you see a weight attached to an organic compound, you know that's a functional group and an alcohol. Another group is a double bonded oxygen attached to a carbon. This is called a carbonyl group. If the double bonded oxygen is at the end of a chain, then that particular substance is called an aldehyde. If that double bonded oxygen is in the middle of the chain, or it is not on the end, then that's a substance called a ketone. Then we can have carboxylic acid groups, vinegar, for example, has a carboxylic acid group attached to it, and that's a carbon with both the double bonded oxygen and a hydroxyl group attached to it. Then there's a group called a main group, and that's a nitrogen with two hydrogen attached to it. Then we have a phosphate group, and the phosphate group is an oxygen with a phosphate or phosphorus and three oxygen attached, and you see that carries a charge of negative two. All right. Let's look at some alcohols, for example. This, if your count has two carbons attached to it, and so our prefix for two is F. You see we have a single bond between the carbons, and so that means that it would be an A N for the alkanes that have all single bonds. Then you see our OH group, which makes it an alcohol. This is F and all, ETH and OL. So it's a carbon with a hydroxyl group attached, and then that carbon is attached to another carbon that has four or three hydrogens. Let's look at propanol. And so prop tells us that we have three carbons, one, two, three. So there are our three carbons, and then here is our OH group or our hydroxyl group. So this is propanol, propanol, propanol. But let's look at an isomer of propanol, and that will be isopropanol. And with isopropanol, you can see that the metal carbon is the one that has the hydroxyl group attached to it. So here's carbon, carbon, carbon, and then the hydroxyl group attached to the metal. So propanol and isopropanol are isomer of one another. They both have the same molecular formula that you can see that their structural formula is very different.