 There's a number of different ways that we can produce alcohols. The first of these is the synthesis of methanol, and you can see that this one is methanol, and it's produced by the reaction between carbon monoxide and hydrogen gas. We can also produce ethanol through the process of fermentation. In fact, this is quite an important process and one that we'll look at in a subsequent video. In this particular process, we start with a simple sugar such as glucose, and through the process of fermentation by microorganisms such as yeast, the glucose is broken down into carbon dioxide gas, in fact two molecules of carbon dioxide gas, and two molecules of ethanol. A third way is through the hydration of alkenes, and we've talked briefly about this as a form of addition reaction when we were looking at reactions involving the hydrocarbons. So you can see for something that I've drawn here such as propene, so this would be propene with the double bond here between the first and the second carbon, and so if we add water across the double bond, then we know that through a Kovnikov's rule we would get a hydrogen on this one, the double bond would be lost and we'd get our OH group over here, and so therefore we would form propenol. So this is another type of reaction involving hydration or an addition reaction, and starting with one of our alkenes in order to produce often a secondary alcohol, but not always. The final one that we want to have a look at in a little bit more detail on this particular video is a substitution reaction, and we can use substitution reactions of haloalkanes to produce alcohols. So here you find I have a four carbon, one, two, three, four carbon organic compound with hydrogen in each of these spaces and a bromine. What happens when we add the water molecule, an HOH molecule, is that we're going to add the OH hydroxyl group into the place where the bromine is currently sitting. That's going to cause a substitution, so the bromine is going to be substituted for the hydroxyl group, and that's going to mean that the bromine is going to come out of our organic structure and the hydroxyl group is going to go in, and as a result of that we will turn what I have drawn here as one bromo butane into butanol, in fact butanol, if it's come from the same carbon. So this is an example of a substitution reaction, so let's have a look at these in just a little bit more detail. So substitution reactions can actually occur under two different types of conditions. The first condition is when the one that I just talked about, which is a substitution reaction with water, but it can also occur in a solution that contains hydroxide ions. So here we have hydroxide ions. The hydroxide ions will again go in and substitute for the halogen, which in this case is chlorine, and it'll produce alcohol and chloride ions. Now one of the important things about this is I've used this R. R is a, I guess, a similar thing to what X is in algebra, and that is R is just an alkyl group. So it could be one carbon, it could be two, three, four, any number, really. And so because we don't specify it, what we're interested in is the general type of reaction that's occurring here, and because this is a substitution reaction, what we're looking at is saying there's at least one carbon here and any number beyond it. But we're interested in the link between this carbon and the chlorine and the fact that the OH group is actually going to replace that chlorine and bring the chlorine out from the organic compound into the solution as the OH group goes into the compound. So that's what will happen if we use a solution that contains a high concentration of hydroxide ions. If we use water, then we can still get the substitution to occur. We can still have the OH group substituting for where the chlorine was, and of course this is not going to be HBr, this is going to be HCl. But what we will have is conditions that require the addition of a catalyst. So this one is not a reaction that occurs spontaneously, certainly not easily, and so therefore if we're going to have this reaction occurring, then we need to add a catalyst to this reaction in order to drive it towards the right. These are two different ways that hydroxyl groups can be substituted for a halogen in an organic compound, and both of those will produce an alcohol as a product of the substitution reactions. Thanks for watching.