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Video transcript

here's the general reaction to form nitrate esters from alcohols so we have our alcohol over here on the left and we react that with some concentrated nitric acid and concentrated sulfuric acid as our catalyst and I believe this reaction is reversible so we could think about that we would form our nitrate ester over here on the right it would also form a water in the process so the water molecule is going to come from this hydrogen on the alcohol and this Oh H on our nitric acid let's take a look at the mechanism to form nitrate esters and so I'll start by redrawing our nitric acid molecule here I think this is the correct mechanism although I try to look up the mechanism in some textbooks and I could not find this mechanism anywhere so I hope that the one that I show you is the correct one all right well if I think about nitric acid and sulfuric acid sulfuric acid is actually the stronger acid so sulfuric acid is going to donate protons and the nitric acid is going to accept those protons the nitric acid is actually going to function as a base so lone pair of electrons on the oxygen are going to pick up that proton so now oxygen has three bonds right two two hydrogen's and one still to this nitrogen here it still has a lone pair of electrons on it which give it a +1 formal charge this nitrogen over here is still double bonded to one oxygen and it's still bonded to this oxygen over here a negative one formal charge and a +1 formal charge like that so that was our first step of our mechanism and acid-base reaction in the next step if we look closely we can see that we kind of have water as a leaving group if a lone pair of electrons on our oxygen move in here to form a new PI bond that can kick these electrons in here off onto the oxygen and water has now left so let's go ahead and draw the results of that right so now we have h2o as a leaving group so h2o has left we now have nitrogen which was double bonded to an oxygen up here it's now double bond to another oxygen down here and it still has a plus 1 formal charge now so this is called the nitronium ion and since the nitrile is positively charged it wants electrons so it's going to function as an electrophile in the next step of the mechanism when an alcohol molecule comes along alcohols have these lone pairs of electrons here we know that negatively charged electrons can function as nucleophiles so the negatively charged electron is attracted to the positively charged nitrogen and nucleophilic attack will kick these electrons off onto your oxygen let's go ahead and draw the product of that nucleophilic attack alright so now we have our R group bonded to an oxygen and our oxygen is now bonded to this nitrogen here this oxygen is also still bonded to a hydrogen giving it a +1 formal charge and our nitrogen still has a double bond to the top oxygen here and it now has a single bond to this oxygen giving this a negative 1 formal charge giving this nitrogen a positive formal charge like that so we've almost formed our nitrate ester if we look at this all we have to do now is an acid-base reaction to take this proton off of our oxygen so water is a is a decent base and a lone pair of electrons on our oxygen can take this proton leaving these electrons behind on this oxygen here and we would form our nitrate ester alright so now we have R with an oxygen and then no.2 like that so once again I think this is the correct mechanism but I'm not 100% sure the formation of nitrate esters has a few very famous examples let's look at the most famous reaction where a nitrate ester is formed let's look at what would happen um if we started with this alcohol as our reactant this is called glycerol or glycerine it has 308 groups on it and if you react glycerine with excess nitric acid and also sulfuric acid all concentrated well we would form a nitrate ester at each one of our Oh H groups so we're going to form a nitrate ester at each of Roh groups to form this as our product right we put nitro groups onto glycerin so this is called nitroglycerin so of course everyone knows about nitroglycerin very famous high explosive it's a liquid it's extremely shock sensitive so it's extremely dangerous nitroglycerin is not something that anyone should attempt to make at home so that's it's not a good it's not a good demonstration for chemistry instructors a much better much better demonstration for chemistry and instructors would be to form another nitrate ester starting from cotton or or cellulose so here we have the cellulose polymer it's made up of a bunch of glucose molecules so here's a glucose molecule here is a glucose molecule and if you stick a whole bunch of glucose molecules together and some giant polymer you form cellulose otherwise known as cotton so if you take a bunch of cotton balls and you mix them with concentrated nitric acid and concentrated sulfuric acid you can you can you can put nitro groups at each one of those alcohol groups you can form nitrate esters so each of these alcohol groups gets turned into a nitrate ester so I can go ahead and put I can put my nitrate esters in you notice there are three nitrate esters for each glucose molecule so we form nitrocellulose as our product otherwise known as gun cotton gun cotton is much more stable than night then nitroglycerin is you can store a gun cotton overnight and if you ignite it it will give you a nice little fireball so it's an excellent demonstration for chemistry students