all right what's up ocam so today's lab uh preparation of aspirin from salicylic acid aspirin is acetyl salicylic acid because we're basically adding an acetone functional group to our acetyl group to the phenol portion of a salicylic acid so phenol remember is a benzene ring with an ohio so it's like an alcohol okay now um lots of stuff we want to learn today so um some heating techniques basically uh heating in a conical vial with an air reflux condenser um and then in addition to that we're going to be calculating our limiting reagents as well as our um theoretical yield and actual yield for this particular reaction when all is said and done um and in addition to that what we will be doing is kind of um going over a little bit of crystallization again we will be crystallizing our product uh to obtain a more pure substance because uh after the reaction is done we'll have some leftover acetic acid phosphoric acid there's going to be some other stuff in there maybe maybe some starting material or what have you so really after that's done what we're going to do is test the purity of our material with the ferric chloride test and the melting point so the melting point we already know that where we know that the melting point gets depressed when we have an impure sample so we're going to see where we lie on that in addition to that we will that ferric chloride test is basically a test to determine it's a qualitative test first of all not quantitative so all we're doing is testing for the presence of salicylic acid with ferric chloride so um all we do is add a drop of ferrochloride to and then if it turns purple you would think a beautiful color like purple would be a good thing but in this case it's not so ferric chloride so the iron cation in there does react and form a metal complex with the phenol in basically any phenol but in this case it's the phenol on salicylic acid so if it does form that makes a beautiful purple color and that means we do have salicylic acid presence now the quantity of salicylic acid is not going to be clear you can't really say just because it's dark or light that you have a lot or a little of salicylic acid just because we're basically eyeballing how much sample we put in there so it's a qualitative test if it's purple we have salicylic acid present so therefore it's not necessarily perfectly pure it's totally common especially in the human environment that we work in in santa barbara but just something to be aware of okay so let's take a look at kind of like what we're doing um the chemical reaction scheme as well as some other little tidbits of information okay all right y'all so today is here's the lecture or some information on the preparation of aspirin which is the today's lab and so really what i'm drawing out is of the reaction scheme so we have salicylic acid combined with acetic anhydride and this combines with an a catalytic amount of acid catalyst so in this case it's going to be h3po4 and then we get our product acetyl salicylic acid which is the aspirin okay so [Music] okay underneath all of these uh well at least salicylic acid i have the mass uh 138.1 grams per mole i have acetic acid 102.1 as well as a density of 1.08 grams per milliliter and then aspirins is 180.2 grams per mole and the acid catalyst is not important because what goes in comes out that's the idea of a catalyst and so um i really just want to point out the fact that the purpose of this concentrated phosphoric acid is basically to create a lower activation energy for the reaction which means that the speed or the rate of this reaction is going to be much faster and it's going to require less heat so we can heat it to like 50 degrees like we are as opposed to like 100 or 200 and it's also going to be much faster than if we were to leave the phosphoric acid out of the reaction okay and so this is typical for catalytic reactions it is an equilibrium as well and so it can go left and right and all right so another thing that we have to do today is calculate the theoretical yield right and so this is exactly why i gave you the molar masses as well as the density of acetic anhydride so let's say hypothetically we had a hundred milligrams of salicylic acid i'm gonna abbreviate that sa uh and then we also had let's say i don't know 200 um microliters of acetic anhydride a a um how much product are we going to get how much acetic acetyl salicylic acid asa are we going to get so what we need to do is determine and determine the limiting reagent and so the way we do that is basically figure out the moles we know that for every one mole of salicylic acid and one mole of acetic anhydride we get one mole of product so it's a one-to-one ratio so basically all we have to do is determine um which compound has the left the smallest amount of moles in this case and so the way we would do that is convert our 200 microliters to uh 0.200 milliliters then we can multiply that by 1.08 grams per ml and we can multiply that by the reciprocal of the molar mass 102.1 grams per one mole of right here so um that basically cancels out our mills cancel out our grams i'll put a here sorry and then we've got [Music] okay and now what we also want to do is convert our zero point our sorry our 100 milligrams of salicylic acid that goes to 0.100 grams of salicylic acid and then we can multiply by the reciprocal of the molar mass 138.1 grams of salicylic acid for one mole of salicylic acid those cancel out and then we get moles of salicylic acid right i'm going to let you do that math but i'm just showing you how to do the calculation because uh word on the street is that's helpful so um in addition to that i'll i mean i'm also not going to show you how to do this conversion because this conversion we should know that already from general chemistry and then once we've determined that let's just say in this case we got i'm gonna do another hypothetical well that's that might confuse you so let me just let's without even calculating the um the number of moles of acetic anhydride let's just assume salicylic acid is our guy so 0.1 divided by 138.1 equals 0.00072411 moles of salicylic acid okay so that means that we would multiply that by uh one mole of acetyl salicylic acid per one mole of salicylic acid and that means that we would have 0.00072411 moles of acetylsalicylic acid multiply by the 180 multiplied by the molar mass 180.2 grams of asa per 1 mole of asa and so that's 180.2 i got zero point one three zero um i'm just gonna leave it like that [Music] acid so we started with about 100 milligrams of salicylic acid and then we should get more in terms of mass just because the mass of the product is greater and we've actually added this acetyl functional group or this portion of the molecule that's why it's called acetyl salicylic acid okay now um it's and one another thing i wanted to kind of touch up on was this actual reaction is called a fischer esterification and it's typically done with alcohols plus let's just do acetic acid in this case and then we have our h plus and what we end up getting is our desired ester product because this guy right here and this guy right here end up piecing out as water and so water is a byproduct but um turns out that esters in the presence of water hence the the equilibrium can actually go back to the alcohol and the carboxylic acid okay so the water does pose a problem and generally in a lab we might we may or may not uh employ methods to remove this water either with some sort of drying agent or something called the dean stark which you'll you'll be will be introduced at another time but either way just wanted to point out the fact that water sucks gatorade's better i mean the water is not good uh for chemical reactions that require the that result in the loss of that product if they're equilibrium because uh the presence of water inherently allows it to move backwards and form the decomposition product okay so this would just be the decomposition of an ester in the presence of water and this is exactly what happens to acetyl salicylic acid or [Music] also happens in our stomach because we do have stomach acids right and obviously water and so it turns out that this guy is actually the active component in our body so basically prostaglandins are kind of compounds in our body that are involved involved in the body's immune response so anytime there's like something going on that your body doesn't like it prostaglandins are involved in a physiological process that um kind of evokes pain or fevers or maybe local inflammation and so aspirin is actually believed to inactivate one of the enzymes responsible for the synthesis of prostaglandins and so specifically arachidonic acid and so that's kind of how the function of salicylic acid works and um some pretty cool stuff arachidonic acid is a crazy structure let me actually just draw this for you just because it's fun boom boom i'm just gonna draw a cray let's see let's see let's see let's see let's see something like that um whoops we gotta have some double bonds in here um and this is arachidonic acid all right all right what we've got here is the ingredients and equipment to get the party started so what i've done here is i've already weighed out that solid powder that's salicylic acid that's 0.208 grams or 208 milligrams of salicylic acid you're going to need that number to calculate your limiting reagents as well as your theoretical yield in the end and then i have on that same uh piece of paper i have my spin vane which will go inside my five mil conical vial which then gets this guy set on top right and so i'll explain that in a minute but we have a pipette to add our drop of phosphoric acid we've got our eppendorf micropipe header to add our acetic anhydride and we're going to be adding 480 microliters aka 0.480 milliliters okay so let's go ahead and take a look at the setup of the hot water bath so what i've done is i already started this oh let's check that temperature so turn that on it's at 51.5 degrees celsius as you can see boom we want it at 50 degrees that's actually perfect we don't want it too high too low above 50 degrees but as you can see i set this up before i even got everything else ready to go and that's exactly what you want to do this is the first thing i set up coming into the lab i got my clamp and then another important thing is that thermometer is not touching the bottom of that hot water bath and so that's what you want as well you want that set up to where it's testing the temperature of the water and not the hot um the hot plate essentially okay so let's go ahead and uh go ahead and get this reaction started we're only heating it for 10 minutes so that's cool all right like i said i've already pre-weighed this solid material out because i mean you know how to weigh stuff out right so basically i will i'll try and pour this towards you and in the camera view but bear with me i'm not left-handed so all right i didn't spill anything yeah what's up ambidextrous or what so um now that we've added that in there we want to add our 480 microliters of acetic anhydride and this is our micropipettor as you can see we have it set to 480 so um that zero that's red sorry let me try and focus this bad boy there we go that red zero is the one that we would have for the 1000 microliters so that means we have four eight and then the zero at the end is not on this particular micropipettor that's just something that we need to be aware of and so think that the numbers can be adjusted with this part right here and so you can see the dial is changing and so that's important that we know how to kind of use this bad boy there's also again i've pointed this out before but there's two points so as you push down to withdraw the liquid that we want so the acetic anhydride in this case you push until there's the first resistance and then you suck it up and then when you're dispensing it into the reaction vial you can actually push it a little bit harder to push it all the way down to make sure that you get all of that acetic anhydride out of the micropipetted tip okay and so that's what i will be doing right now and now we are withdrawing the liquid and now i will be pushing all the way down okay and then i can push this part right here on the micropipe header to release the tip and place that carefully down over here now what i want to do now is go ahead and add a drop of my phosphoric acid just one drop because it is an acid that catalyzed reaction and we don't need that much so i want to make sure i get a full drop though so there we go now i set that down carefully i'm also just separating the bulb from that pipette so we don't get any chemicals in there to ruin that plastic that latex bulb now what we want to do so uh well first you can actually put our spin vane in there that's the triangular one and i probably put that upside down on accident didn't mean to drop that in yet but that's okay it'll still do its job now what we have is our air condenser so notice there's it's basically just an empty tube see if i can look it through look at that so it's an empty tube space that's all it is and um you can see this ground glass portion right here that actually goes right into the vial and so uh this little rubber uh this o-ring right here is what we would call it it's a ring that we just kind of place right over that that portion right there because this can just kind of come in and out as it pleases and we don't want that to happen during the reaction and so we place an o-ring on there and now when i put this vial cap down on it as i tighten it it pushes the o-ring down even further to better seal any kind of gaps that might happen or kind of be created during the heating process and so now i can just kind of hold it right here and it's all stuck together right now these this point right here is not always perfect and so you don't ever really want to depend on just holding it right here because it could sometimes slip through depends on how big this hole is right here okay so what i want to do now is basically place it on the hot plate or the in the hot water bath at 50 degrees for 10 minutes i want to make sure that i start by 10 minutes once we get everything dissolved and kind of situated on the hot plate so i've already got a clamp on here now you want to make sure that that clamp is going to hold the vial nice and low so that the entire reaction is submerged in the hot water bath if it's not you need to adjust it so another thing is you want to make sure that it's not touching the bottom but it's as low as possible right so that basically means you have to have enough water in it not sure if you can see it but i will be turning on the hot plate now and you can see i think you can see that it started spinning and so we want to make sure that we get that spin vein going um to make sure that the reaction is occurring as quickly as possible but also we want to make sure that we get all that solid dissolved now the reaction uh reactions typically occur much faster in a liquid solution and so that's why we do want to make sure that we get that solid material dissolved it could occur in a like a liquid solid interface but that's much slower and we ain't got time for that we want to heat this for 10 minutes okay now notice that these this particular vial is placed more or less above the center of that hot plate that's where the magnet really is spinning round and round right you spin me right around magnet right round like an o chem reaction baby round round all right sorry about that i had to that's what that's how my brain works you know what i mean everything is music to me so um sometimes i i lose my my train of thought but sometimes i don't um where was i oh so basically if it's off centered on this side this side or maybe even forward or backward then it's not going to stir very well so if you're having problems stirring that could be one of the issues it could be that it's not centered on the hot plate but it could also be that you had so much solid material in there it almost formed a cake and that spin vein got stuck in there right if that's the case then you're going to want to go ahead and dislodge that with a spatula or a sprint a stirring rod uh just depends on your preference but it looks like everything is a nice homogeneous mixture so i'm going to go ahead and start that timer for 10 minutes all right all right we're about five minutes in uh reaction hasn't exploded or anything just kidding it wouldn't but you always want to make sure that you're monitoring monitoring your reaction carefully make sure that you want to keep an eye on the level of the solvent to make sure there's no visible carefully make sure that you want to keep an eye on the level of the solvent to make sure there's no visible reduction in that level if there is then maybe you have a leak you can also kind of look at all the seals make sure there's no condensation up in here condensation can occur but you don't really want it to go above like halfway i would say if it does then it might be too hot right now it actually did the temperature did go up a little bit to 60 and it's supposed to be at 50 but that's okay i just wanna i lowered the temperature and then we'll let it keep going um notice i always also did grab some ice for the ice bath the crystallization portion uh as well as i said i set up the vacuum so this is the hersh funnel and that hersh funnel uh has of the filter paper inside of it already so we're actually good to go on that front one thing i want to point out also while we're while we're on the topic is typically in my opinion you should always make sure that that vacuum flask is nice and clean just in case you mess up when you're filtering your product and maybe the filter paper wasn't covering all the holes and you have a lot of product that kind of went through into that filter flask or that vacuum flask and if that's the case you want to be able to salvage that and so the only way you can careful or like do that in a good manner is by having a clean flask and if it's clean basically all you have to do is pour it right back out maybe even maybe redo the crystallization or maybe just filter it right after that and so it is important for your glassware to be clean just in case uh you have you make some mistakes everybody does so we just gotta make sure that we protect ourselves from our own mistakes okay now that i've got about like i don't know three to five minutes left what should i do i've kind of i've worked ahead i'm at a stopping point personally so what do you think your professor does when there's a there's a break what do i do in the lab we'll see at the end of the video probably all right so uh basically it's been our 10 minutes so we want to do make sure everything is all good what we're going to do is carefully raise this out of the heat to remove it from that heat i personally like to uh make sure that it's nice and secure so what i'm gonna do is um just double check everything right here you wanna make sure that you turn off that heat you can also turn off the stereo might as well and let that cool uh to the point where it can be handled honestly it's really not even that hot so what i'll probably do is place that inside of a beaker so maybe something something like this it's more secure it's prevents me and my friends from knocking it down so let that hang out until it gets to room temperature at which point we will obviously remove the condenser we also want to remove that stir that spin vane and then we're going to place it in our ice bath okay so go ahead and sit tight all right so that's definitely okay to handle so i'm going to go ahead unscrew this gently twist if i need to to take that off place that down carefully and then we have our spin vein in there and i want to remove that with my trusty forceps which i made sure nice and clean so as not to contaminate our beautiful reaction okay now uh this honestly feels like it's pretty cool almost to room temperature but i'm gonna let that hang out for another minute before i place that into my ice bath so remember the ice bath is to cool that even further to uh further reduce the solubility of the product in uh in this solution okay and so the slower we let this process occur the better our crystals will be which means the more pure our product will be so we got to be patient all right so boom ice bath you want to make sure that there's it's an ice water bath because that's going to increase the contact of the cold water bath to the conical vial you also want to make sure it's not going to tip over so you can definitely place a clamp around that or you can just place it in a container that's not gonna allow for to tip over okay so we're gonna leave that in there for uh probably a few minutes before we observe to see if we have any crystals for me okay so we should start to see some solid acetyl salicylic acid forming if we don't then what we're going to do is go ahead and scratch it with a either a spatula or a glass stirring rod to create that nucleation site and induce crystallization sit tight oh you can't really see but let me see if i can uh help you sorry about the shakiness apparently i had one too many red bullets at home you know what i'm saying a little red bull action get the day going [Music] a cinch look at that oh looking nice that's the start of it we're grinding and let's see what it look like what did it look like ah i can't tell i'm gonna let that hang out in there for a hot minute probably while i clean up everything else [Music] yo okay pulling up all right so now we got some lovely caristos huh all right so what i did you can see that the volume of this is actually quite high so i added about three ml or so to this reaction vial so that way i could break it up you know there's in this particular reaction we added phosphoric acid which is a catalyst so it should still be chilling in there right uh we also added um acetic anhydride so and that's going to form salicy or i'm sorry that's going to form acetic acid in which we don't want either and so what this water is going to serve the purpose of is to kind of almost wash our product and make sure that we've got a good amount of cleaning going on here so now i'm going to go ahead and take this to the filter all right so i want to make sure that my filter you can hear that i know you can i want to pour a little bit of water on there first to make sure that we get the filter paper nice and stuck on there so i'm going to go ahead and create a little suspension stir that up and then quickly pour that off quickly and carefully kind of get the rest of that material off okay and now what we want to do is i didn't get to show you but i kind of set aside some cold water it's ice water and so the reason for this is because we don't want our what's it called we don't want our we want to wash our clean product with about three or four portions of cold water and because aspirin is soluble in water somewhat we want to make sure that we don't dissolve our product and lose it it's very very possible that we will do some in this step but that's okay as long as we obtain a nice clean product and what i'm going to do now is leave that on there for about 10 minutes to let it dry and then we can go ahead and test it the melting point as well as our ferric chloride test it doesn't need to be dry for the fair quality test but i'm gonna let it dry anyway okay so while we're waiting for the um salicylic or acetyl salicylic acid aspirin to dry we can do the ferric chloride test as i said so uh what we're about to do here is set up three test tubes one's gonna be a control uh well i guess two of them kind of are to some extent uh we're gonna have one with water about a half a mil um totally estimating i'm not the type of person that could just like eyeball well maybe i can sometimes i have all half a mil but sometimes the half milk doesn't it doesn't matter really we want to make a solution of one of them with salicylic acid so i'll go ahead scrape a little salicylic acid um there you can't really see i got a tiny spatula full doesn't matter again basically i want to get some inside of here you can see it chilling on top uh we've also got uh water and this one okay and this middle one i'm gonna make my sample so the middle one is uh the one we don't want to turn purple we also don't want the water one to turn purple the salicylic acid does definitely turn purple and we want that to occur so i need to make sure that this is dissolved before i do that test and then i also need to get a spatula to get my solid material out okay so let's see if we can get a little bit of sample i want to make this about the same amount of sample that i put in for the salicylic acid so it's on a spatula you can't really see it um maybe i'll put a little bit more just for just for good measure as my son would say just because i say plus i i have plenty in there um i know it's going to take away from our yield in the end but i don't really care that much because that's basically the source of error when we talk about it in our write-up that's what we're going to say okay so we want to make sure that that is definitely dissolved in the water okay and then we can get to going okay i'm a little impatient so let's just go ahead and get started and see what happens okay so remember this one right here that's salicylic acid that's my sample and that's just water so we do not want um the two the water and my sample to turn purple so let's go with the salicylic acid we'll add a drop of the ferric chloride and watch the color change so gorgeous so gorgeously purple now oh yeah you can see nothing going on nothing going on obviously we still see some solid in there but i'm mixing it in there pretty good uh clearly the the iron complex that forms the purple color is very soluble and so uh it would be forming if it was if we had a good amount of salicylic acid in there you could technically get like a very light pink color but it's not very obvious to me um remember this is a qualitative test um and so but i mean we can't even say that this is colored at all so i don't know it's almost like i do chemistry or something and i didn't get any um starting material in there so i want you to basically talk about [Music] this type this in your discussion um what does this conclude what does this kind of tell us in the end and then um did we see what we should have seen did what was the you also need to talk about your theoretical yield your actual yield and then your your errors associated with the experiment obviously my errors or potential errors we do we are probably going to have a loss to that um we have our theoretical yield what was the percent yield and why was that different than 100 if it was we're going to get a melting point what is that melting point going to be is it good is it where it needs to be compared to literature value [Music] things like that so there's obviously more things that you can put in your lab report to discuss this experiment but those are just a couple ideas now i feel like i want to go take a melting point of this okay all right so remember we gotta get our um melting point apparatus set up so let's do start temp we probably want to bring that up to like 100 maybe even 105 or so just because our melting point of salicylic acid is in the 130s and so we don't want to i'm going to do this actually 110 i'm trying to be here forever and i know that the product is pretty good pretty clear clean so um that's pretty much it i'm going to go ahead and click start start again that gets the preheat going and then once it gets up to 105 or 10 it's going to say ready and then we can go ahead and add our sample let's go make our sample oh pretty basically um smash smash smash smash got a little bit in there we got good enough um now what we want to do is go ahead and tap that on the counter and we got some down there and so we are good to go all right so there it is it says well ready so i'm going to go ahead and click melt or start the melt light came on and now we can see sorry our sample inside of that window and we'll keep a close eye on it over time and um yeah that's it i wish i was fancy i knew how to like get two videos going on right here for you guys it could be like this i'll do like this a yeah here i am so i guess i should tell you guys some stuff about melting point remember what do you what is some stuff you remember hopefully you remember that there is a melting point depression if we have some impure samples so um if we let's say we said our salicylic acid supposed to melt around 138 then um and it melts at like 125 why would that be well that would be because we we had that significant depression in that melting point because we had some impure sample what could that impure what could that impurity be it could be a variety of things it could be starting material it could be some reagents that we use to work up the reaction such as like water or something like that it could be acetic acid it could be phosphoric acid etc so anything that had ever touched the material from the beginning to the end that can be a source of impurity the water would be just because of the wash with the filtration maybe it wasn't done long enough this stuff was sitting here for quite a while so i think it'll be looking pretty good um but basically that's the melting point depression and it's yeah it's usually a pretty good indication of uh of the purity of the sample although just because the depression occurred doesn't mean that it's like a bad impurity for example it could just be water which means we have to dry it longer and so not a big deal sorry i'm trying to like [Music] wow 125. i don't really see anything going on how are you guys today i'm good i'm good it's real hot what's up with the heat i don't like it i get one bit and i don't think they want to have air conditioning in this particular lab because i'm in this lab probably that or maybe it's just in general air conditioning there's a struggle around here so let's see we're at 128.5 there it goes come on buddy come on buddy let's see what you got here i don't really see anything going on folks not a thing maybe a little something on the bottom so let's check out that 131.5 ish it's hard to see through this camera i'm looking at the ipad um but yeah it looks like something's going on right we're at 132.8 now i want you guys to decide on what your melting point is so there it is there's the temperature for you let's saw some move there's 134.3 well i'll tell you when we're at 135. okay so we are at 135.0 now we 135.5 135.6 i'm sorry 136 jk and then we are at 136.5 1 37 137 and 137.5 oh my goodness 138 okay 139 139.5 and i'm going to stop at 140. boom baby that's a long lap i must say um there was somebody down there so basically um that's it it's a wrap go ahead and um you don't have to watch the rest of this video it's just for fun so that's all the information you need bye ow so this is something that um i'm gonna give credit to another student but um it's a joke about arachidonic acid but i gotta remember it so i mentioned that arachidonic acid kind of sounds like a dinosaur to me dinosaur what's up and as i kind of wanted to see what kind of people could think of in terms of jokes about arachidonic acid um and somebody came up with a good one and it was um why did the why did the dinosaur take aspirin because he was pronto oh my god that's so good that's fire right there that's money i had to give credit to that student not going to any of the names but uh this is fantastic it's a great joke i'm sorry [Music] because the way that the sky opens up when we touch it it's making me say that the way you hold me hold me on feel so holy holy holy holy [Music] [Music] holy it's not appropriate [Music] [Music] is [Music] sometimes