[Music] [Music] hey everybody welcome to the steam distillation lab here's the outline for this video i'll be going over the experiment in general focusing on the steam distillation technique then i'll show the experiment in the lab and at the end i'll be going over some nmr concepts in this experiment we are going to be steam distilling cinnamaldehyde from ground cinnamon so i'm going to spend some time going over that technique in steam distillation we are able to separate volatile organic compounds from leaves or seeds or even like inorganic salts just by boiling them with water and the reason this works is because when two immiscible compounds are placed together their vapor pressures are actually additive so in this case we will have cinnamaldehyde the organic compound that isn't very miscible with water and the total vapor pressure of the system of the two phase mixture will actually be the sum of the vapor pressures of each pure compound the cinnamaldehyde and the water since the total vapor pressure is higher than each compound's respective vapor pressure both the cinnamaldehyde and the water will co-distill at a temperature that's actually lower than water's boiling point here's an example of how this works using iota benzene which has a boiling point of 188 degrees celsius its vapor pressure at 98 degrees celsius is 46 torr and the vapor pressure of water at 98 degrees celsius is 714 torr together those add up to 760 torr which would be equal to the atmospheric pressure so this compound will co-distill with water at 98 degrees celsius rather than its usual boiling point of 188 so this is a huge advantage when using steam distillation because it allows us to distill organic compounds without decomposing them in our case cinnamaldehyde has a boiling point of 248 degrees celsius but it decomposes at that boiling temperature and it can oxidize into cinnamic acid instead if we boil it with water it will coat a still at the boiling point of water or even slightly lower another cool aspect of seam distillation is that we can pretty easily separate organic compounds directly from their source and this is what essential oil companies do all the time for example limonene is an organic compound that gives the fragrance of oranges and is often used as a flavoring agent as well but it can easily be separated from orange peels using steam distillation in our experiment we will be checking out a 50 milliliter erlenmeyer flask with a specific joint that can attach to the hickman still and you can just grab that from the stock room then we'll add the ground cinnamon to about 10 to 15 milliliters of water and begin boiling it and we'll also be using triton x45 as a surfactant since it lowers the surface tension helping the water boil not as violently so that we don't get cinnamon up into the hickman still as well here's a look at that compound the n here representing a given number of ether groups attached together in a chain so for triton x45 there would be on average between four and five ether groups attached together and with that many oxygens triton x-45 is pretty water soluble so it won't contaminate the cinnamaldehyde water distillate that comes off during the steam distillation process as the mixture boils a milky cinnamaldehyde water distillate will start to gather in the hickman steel so the water and cinnamon will be boiling in the erlenmeyer flask and the distillate will start to rise condensing and gathering in the base of the hickman still and then we can remove it from there using a pasture pipet we'll gather about five to seven milliliters of that distillate into a separate test tube then we'll extract cinnamaldehyde out of that distillate using methylene chloride and we'll do three extractions then those extracts can be dried with sodium sulfate and the solvent evaporated this will leave us with a pure cinnamaldehyde product which we can weigh to calculate a percent recovery we won't be calculating a percent yield because we didn't do any reaction with multiple ratios to worry about so the percent recovery will just be the weight of cinnamaldehyde isolated divided by the weight of cinnamon used multiplied by 100. and finally we'll characterize that product by running an ir spec [Music] okay here is the erlenmeyer flask rented from the stock room i've already placed a spin bar inside so now i'll add between 10 and 15 milliliters of water then i'll add 10 drops of the triton x45 doing all of this before adding the cinnamon because adding the cinnamon last can help keep it from burning on the bottom of the flask initially now i'll weigh out about 2 grams of the ground cinnamon noting exactly how much is weighed so a percent recovery can later be calculated and i'll just add that on top of the water in the flask [Music] now i'll set up the apparatus attaching the hickman still and a water condenser on top of the erlenmeyer flask and then start heating things up as it does warm up you can actually start to see the milky distillate in the cinnamon and as that begins to boil we're going to see that a lot more on the sides of the flask eventually the distillate will start to condense in the hickman still and when the base fills up we can begin gathering it using a pasture pipette be careful to monitor the cinnamon because we don't want it boiling up into the hickman still so if it starts getting close a lot of air can be used to cool the flask down right now it's actually not an issue but i just wanted to show what to do if it did start boiling too violently it looks like enough distillate has gathered in the hickman still now so i'm going to go ahead and start removing it and transfer over to a test tube i'm going to keep doing this until i've gathered 5 to 7 milliliters of the distillate and i have a separate test tube filled with about seven milliliters of water as a reference so i'll keep going until it matches that after doing this about eight or nine times over 20 minutes i think i'm on the last one and it should match up with the water level now i'm good to move on so i'm going to start getting some methylene chloride to do the extractions but before adding it to the test tube i'm going to rinse the apparatus to collect any cinnamaldehyde that would be adhering to the glass surfaces then i'll just remove that from the hickman still and add it to the test tube containing the distillate now we can see the organic phase below the aqueous one so i'm just going to add a little bit more methane chloride mixing the two phases together really well and then transfer the organic phase over to an erlenmeyer flask before moving on to the extractions though i'm going to start working on cleaning up the apparatus so that the remaining cinnamon doesn't completely coat and burn onto the bottom of the flask i'll add a little bit more water and keep it warm on the hot plate scraping the cinnamon off of the bottom of the flask and then disposing of it in a bucket specifically designated for the cinnamon waste you can see that there is still some burnt residue on the bottom of the flask that i'll need to clean off so i'm going to add some more water and add about a gram of sodium carbonate and heat up the solution to help remove that burnt residue the solution can be allowed to boil but be careful because if there's still a good amount of cinnamon left it can actually boil over and come out of the flask so just monitor it and don't leave it there and a spatula can be used to help scrape off the burnt cinnamon and this should be continued until the erlenmeyer flask looks just as clean as it was initially now i'll continue with the extractions adding methylene chloride mixing the two phases and transferring the organic layer to the erlenmeyer flask and i'll do this a total of three times once the extracts have been gathered i'll dry that organic phase over some sodium sulfate and i'll add that until it's free flowing then i'll transfer that solution over to a beaker and since i used quite a bit of methane chloride i'm transferring it to a beaker rather than a conical vial although a conical vial would probably be preferred and i'll rinse the sodium sulfate with some additional methane chloride to help reclaim more product the solvent can then be evaporated using a stream of air and gentle warming until just the cinnamaldehyde liquid remains i'll weigh out the full beaker containing the isolated product and use that to spot a salt plate so that an ir spec can be run and that turned out really well there are a wide range of peaks identifying the product we have the aromatic hydrogen peak at 3335 a group of peaks above 3000 for the hydrogens attached to the alkene the two aldehyde peaks at 2814 and 2742 a carbonyl peak at 1677 and a peak at 1626 for the carbon-carbon double bond finally i'll weigh out the empty beaker to get the weight of the cinnamaldehyde isolated [Music] okay i wanted to go over a few things that should be helpful when analyzing the nmr spectra for cinnamaldehyde the first thing that we should recognize is that this molecule is fully conjugated and there's going to be lots of resonance that will actually have a pretty strong effect on how shielded or de-shielded the hydrogens and the carbons end up on this molecule so let's go ahead and consider those resonance structures the carbonyl group would be electron withdrawing so electrons would be pulled onto the oxygen to form this first resonance structure then the double bond next to it will compensate by moving over to form this resonance structure and then we can just continue down the molecule moving the pi bonds over and continuing to draw the different resonance structures as we do this we can see that certain carbons have positive charges placed on them so if we look at the hybrid structure any of the carbons that had a positive charge placed on them in one of the resonance structures would now have a partial positive charge placed on them this means that these carbons and the hydrogens attached to them would be more de-shielded because they have less electron density around them to shield them from the applied magnetic field so for example if i look at these two hydrogens attached to the alkene this hydrogen would actually end up being more deshielded because of that partial positive charge even though the other one is closer to the carbonyl group the same principle can apply to the hydrogens on the aromatic ring but make sure to use all the other tools to analyze the peaks and identify which peaks go to which hydrogens i also wanted to go over some concepts that have to do with splitting so to do that i'm going to look at this example from the post-op questions and i'll be focusing on hydrogen 5 so we can simplify it and just look at it like this hydrogen 5 has two neighbors so we might assume that it would end up as a triplet but something else is actually happening here if we look at the two neighbors hydrogen 6 would be cis to hydrogen 5 across that double bond and hydrogen 7 would be trans to it since hydrogen 6 and hydrogen 7 are unique enough from each other they would actually have different coupling constants and would each split hydrogen 5 differently to show this maybe a little bit easier let's take a look at the splitting tree for hydrogen 5 hydrogen 5 is split a certain amount by one of the hydrogens and that distance is called the coupling constant represented by the letter j in this case this would be the coupling constant for the trans hydrogen which usually ends up being between 12 and 18 hertz then hydrogen 5 is split once again by the other hydrogen and this distance would now be for the cis coupling which usually ends up between 6 and 12 hertz since the splitting for trans hydrogens is a lot wider than the splitting four cis hydrogens we don't end up with a triplet as we can see here there are four distinct peaks that would be formed so if we look at the h and mr hydrogen five would end up looking like this and we call this a doublet of doublets from this we can actually calculate the trans and cis coupling constants using the ppm values for each peak so i'm going to go ahead and transfer those numbers to the bottom of the splitting tree that we created earlier and then if i wanted to calculate the cis coupling constant i would just need to measure this distance here and i could do that by subtracting this number from this one or i could subtract this value from this one because that distance would be the same then we can find the coupling constant for the trans hydrogen the problem is there's no value below this line but it should be right in between these two numbers here so we can just find the average between those two and then do the same thing on the other side finding the average between these two numbers once we have that we can then just subtract this value from the other to get the trans coupling constant or we could recognize that this splitting here would be the exact same as this one meaning that this distance is identical to this one therefore if i wanted to calculate the trans coupling constant i could just subtract this value from that one or do the same thing on the other side subtracting this value from that one now we'll want these coupling constants in the standard unit of hertz but currently everything on the hmr has been converted to ppms and this is done by taking the frequency of the signal in hertz and dividing it by the applied spectrometer frequency in megahertz therefore parts per million because megahertz are one million times the magnitude of hertz so if i wanted to get the signal back to hertz i could just take the ppm value given and multiply it by the spectrometer frequency which in this example would be 300 megahertz now i'm going over this splitting because the same thing is going to happen on cinnamaldehyde if we look at this hydrogen here it sees this neighboring hydrogen across a double bond but it's also coupled to this one because it's on a neighboring carbon and since these two hydrogens are fairly unique they'll each have different coupling constants and will each split this hydrogen differently so if we look at the hmr for cinnamaldehyde that hydrogen will actually end up as a double of doublets shown here and that's all i'm going gonna go over i'm gonna leave the rest of the pica signing to you now you