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Here we’re gonna look at a pretty standard pretty basic household medicine house on painkiller called aspirin now before we get into aspirin itself first look at how it sort of came about you know many years ago it was discovered that there was this naturally occurring substance called salicin and this naturally occurring substance could in fact be used as a
Painkiller now there are a few chemists who tweaked the structure of salus and slightly to produce something called salicylic acid and it was found that salicylic acid was in fact an even better painkiller than salicin however salicylic acid proved to irritate people’s stomachs should people ingest it and because it was an acid it would really irritate their stomachs
And so although it was a very good painkiller it wasn’t always the greatest and so what a few more chemists did a few years later is they again they tweaked salicylic acid again to produce something called acetyl salicylic acid so acetyl salicylic acid is what we know today as aspirin so this is our standard aspirin you know salicylic acid itself is not in fact a
Painkiller however what we can do is we can take aspirin we can take acetyl salicylic acid it will pass through our stomach and then once it reaches our intestine it can react to produce salicylic acid and then the salicylic acid is never in our stomach so it’s never an irritant to us and we can then absorb it into our bloodstream and it can act as a painkiller now
Over here we’re gonna look at ways we can do s– acetyl salicylic acid from salicylic acid now here we’ve got the chemical structure of our cells – like acid here we’ve got the chemical structure of ethanoic acid so what we can do is if we take a molecule of salicylic acid we can react it with a molecule of ethanol acid in order to produce our aspirin so i can do
Here is this this these molecules react via a condensation reaction which is also in fact an ass tariff occation reaction so as you can see in green we’ve got two hydrogen atoms and an oxygen atom so they come off they produce a water molecule so that’s why we call this reaction a condensation reaction because they’re splitting off this smaller molecule here then
With what’s left we have something very similar to ourselves to the acid molecule so still get our carboxyl group up here however this time we have an ethyl group or an acetyl group coming off like this via an ester linkage so that is why we call it an esterification reaction because we are producing an ester linkage through yeah so that is our new ester linkage
So that’s that’s the what why there’s one way we can produce acetyl salicylic acid or as we can also call it aspirin so react salicylic acid with ethanoic acid to produce water and aspirin however the problem with this is because we are dealing with an ester linkage here we know the ester linkages are very vulnerable to hydrolysis so an ester linkage if we react
Any molecule containing an ester linkage with water then the water molecule can break down the ester linkage and basically what will happen is in the case of this reaction the reaction will go backwards if we react aspirin with water then this ester linkage will break down and we will produce a molecule of salicylic acid and a molecule of ethanoic acid and so that
Means that if we’re trying to produce aspirin by this reaction because we are producing water the water and the aspirin that we’re producing is then reacting our then reacting together to to react if you react backwards and so what happens is we get a very low yield and a very slow rate of reaction because the stuff that we’re producing is then reacting back into our
Original starting products and so it takes a very long time and it has low-yield so there is in fact one other way another type of reaction we can use to to produce aspirin so here we’ve got again got salicylic acid however over here rather than ethanoic acid were reacting our salicylic acid with ethanoic anhydride now ethanoic anhydride is an interesting molecule
It’s produced by reacting to ethanoic acid molecules together so if i just quickly draw two molecules of ethanoic acid instead i’ve got some hydrogen’s there if we draw another molecule of ethanol acid then what happens these two molecules can undergo a condensation reaction whereby a water molecule is produced so we get rid of that hydrogen and we get rid of this
Hydroxyl group we produce a water molecule and then what happens is we now have this oxygen here still we’ve now got that oxygen here still and so we get this new product so get this new product called ethanoic anhydride so we get what happens is the two bond together like this to produce our ethanoic anhydride molecule so that is help so ethanoic anhydride can be
Produced by reacting two molecules of ethanol gas together that produces ethanoic anhydride and a molecule of water so obviously that reaction doesn’t always fully occur by itself it requires certain chemical more chemical equipment and processes in order to sort of suck up effectively suck that water molecule out of acid molecules but here we’ve got salicylic
Acid and ethanol and hydride and what can happen is again this is a condensation reaction so what’s happening is we’re reacting salicylic acid with ethanoic anhydride what we’re producing is we’re producing some aspirin with the same structure as above however the stuff written in green over here is splitting off by itself to produce another molecule of ethanoic
Acid so simply we’ve still got the ch3 group here and we’ve still got the c bonded to the oxygen however this hydrogen here is coming around on to this oxygen to turn it into a hydroxyl group and now we have ethanoic acid and so in that way if we react salicylic acid with ethanoic anhydride we can produce aspirin and ethanoic acid and of course if we then want to
Get the aspirin we have to somehow separate these two products so we obtain pure aspirin now unlike the reaction with ethanoic acid the reaction with ethanoic anhydride produces a much higher yield because we don’t have that backwards reaction effect that we have up here when water is being produced so this is a much more effective and efficient way of producing
Aspirin if we react salicylic acid with ethanoic anhydride instead of with ethanoic acid so that makes this reaction a much better way to produce aspirin now if we want we often want our painkillers to be soluble and although it is an acid although it has a carboxyl group our aspirin molecule here is not actually very soluble in water so one way we can counter
This one way we can make our aspirin soluble is that we can convert the aspirin molecule that we have drawn here into a sodium salt so basically what happens is if for example we were to remove this hydrogen here as in a a standard a hydrolysis reaction or a standard reaction if this acetylsalicylic acid molecule acted as an acid and lost that hydrogen atom then we
Have a negative ion this whole molecule here would in fact be an iron with one negative charge so what we can do is we can reflectively replace that hydrogen that was here with a sodium iron and so because this is now an ionic compound now we have a sodium iron bonded to an iron that has that was produced from the acetylsalicylic acid molecule we now have an ionic
Compound rather than an acidic compound and so this ionic compound is like all the ionic compounds dissolve in water so basically what’s happening is we’re really bonding the sodium at the sodium ion with the with the other major iron and so we have a structure that looks like this we have a sodium ion bonded to this oxygen there via an ionic bond and so now this
Is a sodium salt version of aspirin which makes it and the soluble because it is an ionic compound because it is a salt so that’s a way we can we can make aspirin soluble we can change it slightly we can ditch that hydrogen here and replace it with a positive sodium ion and therefore our we can we’re converting it to an ionic compound which is soluble now lastly
A new type of a sperm that is being produced in the research is a polymer version of our regular aspirin molecule so here we’ve got we call this wholly aspirin and so the way that this is the way that the way pali aspirin is produced is we have our acetylsalicylic acid here just as usual we have our hydroxyl group there we have another one yeah and sorry in the
Middle between these two things we have what’s called a die acid and so a die acid is basically an acid with a carboxyl group at both ends so what we have is we have a long chain of carbons in the middle and then we have a carboxyl group at this end we have our long chain of carbons then we have a carboxyl group at this sense this is a die acid it has two carboxyl
Functional groups so what can happen is that we can only get this convert this we can have a condensation reaction here where we split off two molecules of water so that hydrogen and this hydroxyl group then the same on this side and so what we get is we get a molecule of water there we get a molecule of water there and we form another ester linkage so if we draw
It so what we get is this structure yeah so we get an ester in kids like that which is drawn a bit haphazardly there and we get another ester linkage like that so if we were to tighten up a drawing then it would look like this then we have this long chain of standard stock standard carbon or ch twos in the middle and so we just have a chain like that and so on in
The middle and so now we have two s linkages funny – salicylic more acid molecules – one die acid and then what can happen here is if we have lots of these monomer units these can bond together so if we have another molecule of salicylic acid here and if this molecule of salicylic acid is really just in the same spot as is in the same spot as this one here so we’ll
Say that this salicylic acid molecule is in fact bonded via and ester linkage to its own die acid off the page here so it’s bonded to it out here via an ester linkage lock-in happens as we can get in fact get a condensation reaction between these two salicylic acid molecules like this so if we get we split off another water molecule there what we end up with is
Something that looks like this we get the two salicylic acid molecules bonded via a single oxygen and then we can create a long polymer like that and so that is the structure of poly aspirin now there are few really interesting really really good features about poly aspirin that are sort of being pursued firstly poly aspirin because it’s a polymer it’s going
To break down slowly it’s gonna break down slowly and that means that if we want to slowly or can slowly release or control the rate of release of the aspirin of the painkiller into our bloodstream then we can inject then we can take ingest yeah a specific type of poly aspirin such that we can control how fast it’s released so we can get a controlled release of
Painkiller as we require which can be much more beneficial and we can get much more sort of controlled and accurate and and useful painkiller or pain-killing up thank youing effects as a result of this poly aspirin molecule secondly like other polyesters this is of course a polyester as its polymer made from this esterification lee ester linkage so it’s a polyester
And like other polyesters and can be made into a thread and so if we use poly aspirin as a thread we can we can use it for stitches and stuff like that and so not only will we have a stitch a type of stitching thread that will break down naturally in the body but it will also provide pain killing at the site of the stitches lastly not only does poly aspirin have
Pain killing properties it also promotes grown bone growth so if people have bone or joint injuries not only will poly aspirin if applied to the bone promote bone growth but it will also kill any pain that is resulting from the injury so it promotes bone growth so now this that’s another a third type of asthma we’ve got our regular acetylsalicylic acid we’ve
Got our soluble sodium salt version and we’ve got poly aspirin now – you seem to note here if we look at the regular aspirin molecule that in fact the way that this is broken down in the body is by hydrolysis so we know that we ingest acetyl salicylic acid it passes through our stomach into an intestine and in our intestine that acetylsalicylic acid reacts with
Water it hydrolyzes and that what that water does is it breaks down this ester linkage just like in the backwards reaction of of the dodgy way that we can produce a single cell acid just like when we reacted salicylic acid with ethanoic acid we produced water and aspirin and that water that water and that aspirin reacted together to undergo a backward or a reverse
Reaction so in our stomach we get this aspirin molecule reacting not in our stomach sorry in our intestine we get this aspirin molecule reacting with water we get hydrolyzing and what that does is it breaks down the ester linkage and so what we end up with is we end up back where we started with a molecule of salicylic acid and of course a molecule of ethanol acid
So even if the spirit is produced via a reaction with ethnic and hydride rather than with ethanoic acid when the aspirin is hydrolyzed in our intestine we’re going to end up with salicylic acid and we’re gonna end up with a byproduct of that hydrolysis reaction some molecules of ethanoic acid so that’s how aspirin is produced that’s a little bit how it works and
It’s different forms and how our body manages to break it down
