 Fossil fuels like petrol, diesel and even LPG are nothing but alkanes and burning alkanes liberates carbon dioxide, right? Now carbon dioxide is not good for our environment, carbon dioxide causes global warming. So if you want to avoid this, we need to remove this CO2 from our atmosphere, right? Now one of the ways to do that would be to plant more trees, well I don't have a tree out here, what I have instead is a mustard field and I'll tell you why I choose this. One of the ways would be to plant more trees and these trees will take in the carbon dioxide for their photosynthetic process and this is how we can remove CO2 from our atmosphere, right? However, wouldn't it be even more wonderful if you could somehow make alkanes from plants, right? We can then use these alkanes to drive our cars and these cars will liberate CO2 and this CO2 will be taken back by the plants again and this is actually going to make the whole process carbon neutral, carbon neutral. So what do I mean by this? Well carbon neutral means whatever carbon that I'm emitting into the atmosphere it's going back into my, I'm taking it back. So there is no net carbon emission during the course of the process, right? So it will be wonderful if you could make alkanes from plants. So can we even do that? Let's see. Well it turns out that vegetable oils like mustard oil or soybean oil, it turns out that these vegetable oils are actually made up of triacylglycerols which are actually a form of esters. They have a long carbon chain that is connected to an ester group and it turns out that these esters can actually be easily converted into acids simply by adding water and these acids can then be converted into alkanes via process known as Colbs electrolysis, Colbs electrolysis. So what Colbs electrolysis does, so what it does is it converts an acid in which we have an alkyl group attached, it converts an acid into a symmetrical alkane. This was this process was first described by Harman Colbe in the late 1850s so we know this process for quite some time. So how do we carry out this electrolysis? Well what we do is we take some water and to this water we actually dip in some metal rods. So these are metals, metals because they can conduct electricity and we call these metal rods our electrodes. Now these metal rods, these electrodes are actually connected to a battery. Let's say this one is connected to the positive terminal of the battery and this one is connected to the negative terminal of the battery. Now because this terminal is positive so it's electron deficient so it actually tries to pull electrons from this metal rod towards itself. While on the other hand because this terminal is negative so it actually has excess of electrons so it actually tries to push electrodes into this metal rod. Now of course don't think that there is any current flowing out here because both of these electrodes are not connected to each other. There's nothing going on out here as of yet. So the circuit is actually incomplete, right? Anyways what we next do is we add some of our acids, some of our fatty acids, our COH to this solution. Now acids especially when these alkyl chains that they have are large. These acids are actually insoluble in water. For example only really small acids like say acidic acid which is CH3COH or something like say propanoic acid. Only these really small acids are actually soluble in water but as I keep increasing this carbon chain the solubility keeps rapidly decreasing and when we go out to something like say hexanoic acid, hexanoic acid will have 5 carbons out here, right? So when we go to something like hexanoic acid it becomes almost insoluble. Now this is because this alkyl chain that is attached to our acid, this alkyl chain is non-polar, right? Now because it's a non-polar it won't dissolve in a polar solvent like water. There's a very famous rule in chemistry. I'm sure you must have heard of it like dissolves like. So polar things get dissolved in polar solvents while non-polar things get dissolved in non-polar solvents, right? So therefore this non-polar alkyl part that is attached to COH is actually hydrophobic it doesn't dissolve in water and greater the number of carbons that we have more insoluble it will be, right? So therefore to make these things soluble in water what we do is we actually add a base to our acid we actually add something like say sodium hydroxide and this base can actually deprotonate the acid it can remove the hydrogen from an acid and this will lead to the formation of a salt, right? So we will get a carboxylate ion RCO-NA+, along with the formation of some water, right? Now this is a salt it's an ionic compound and this will be soluble in water, right? Water soluble. So therefore what we do is we take our acid and we also add some base to it. Now if you do that ultimately what we will be left in our solution is nothing but let's move this out here what will be left will be actually loads of carboxylate ions RCO- along with loads of NA+, and loads and loads of water, right? Okay now once we do all this once we are ready connecting all our connections and everything what's going to happen is that these negatively charged ions which are like flowing in the solution once they come in contact with this electrode which is connected to the positive terminal of the battery because it's electron deficient and it wants electrons so what's actually going to happen at this positively charged terminal is that this carboxylate ion that I have RCO- let me highlight the lone pairs of this oxygen atom this RCO- at this positive terminal can actually lose an electron it can actually get oxidized to form RC- double bond O and an oxygen radical out here, right? So at the positive terminal the carboxylate ion actually gets oxidized to a carboxylate radical and this electrode where the oxidation is actually happening we actually have a name for this electrode we call it anode so anode is the electrode where oxidation is taking place and during electrolysis it's actually the positive terminal of the battery. Now once this radical is formed as you can see this oxygen atom now becomes electron deficient and as you must know oxygen is a highly electronegative element it loves electrons so it's obviously not happy with the state that's currently in so what's going to happen is that this bond is actually going to break so this will form an R radical and a C radical and both of these electrons can then combine to form a carbon dioxide molecule, right? Now this process actually happens very rapidly the moment we have an RCO radical it actually rapidly breaks down to give me the R radical along with the formation of carbon dioxide. Now of course there won't be a single radical formed, right? There will be loads of carboxylate ions going and forming loads of radicals and these radicals that are formed can then combine amongst themselves to form our symmetrical alkanes, right? Symmetrical alkanes. So this is how we carry out Colb's electrolysis which gives us an alkane along with the formation of carbon dioxide let's not forget the carbon dioxide at our anode, right? Now while we are at it let's also take a quick look what's happening at this negative terminal at our cathode. Now the cathode is negatively charged so you might expect that these positively charged Na plus ions can go to cathode and they can accept these electrons and get reduced to Na, right? So at our cathode let's come out here so at our negatively charged terminal which is our cathode in electrolysis you might expect the Na plus ion to get reduced to accept electrons and get reduced to Na, right? However this is not what happens it's actually these water molecules, these loads of water molecules that we have it's actually these water molecules that gets reduced that gets reduced to hydrogen. Now to really understand what's actually going on out here we need to understand something called the reduction and oxidation potentials of various substances of various molecules and we won't go into detail of this in this video but one way to think about it is that these Na plus ions these Na plus ions they have a stable octet, right? So these Na plus ions actually do not want to get reduced to Na so that reduction potential is actually very very low it's in fact lower than that of water so it's actually the water that is going to get reduced to hydrogen gas. Now the same thing is also happening at the anode can also happen at the anode water can also get oxidized water can also get oxidized to oxygen but it turns out that the oxidation potential or the tendency of the carboxylate ion to get oxidized is much greater than that of water so it's the carboxylate ions which gets oxidized. Okay so if you look at our full reaction cobs electrolysis forms an alkane and carbon dioxide at our anode so this is what happens at the anode and it also liberates hydrogen gas at the cathode, right? Now even though this process has been known since 1850s but because it involves radical formation so it also suffers from the same limitations as other free radical reactions. For example this radical that is formed instead of going ahead and colliding head on with another radical to form our alkane to form butane instead of doing that this radical can also collide against these hydrogen atoms of another radical and they can abstract this hydrogen atoms to form to form a different product to form an ethane and an ethene, right? So we'll also get loads of side products in fact so the CH3-CH2 radical can also combine with a carboxylate radical as it's get formed so the carboxylate radical can also combine with CH3-CH2 radical and this will lead to the formation of some esters, right? So there are loads of side products that we can get so it's not a really good way of preparing alkanes the yield will be low however having said that because alkanes from petroleum products are non-renewable and we're going to run out of them pretty soon so using alternative sources like vegetable oils are actually becoming more and more mainstream and this whole coal-based electrolysis can actually be driven by solar energy and there is currently research going on in increasing the efficiency of these cells so that we can get more of our alkane products so coal-based decarboxylation seems to have a bright future ahead