Benzaldehyde smells like almonds or cherry candy and for this reason, it's often used as a flavoring agent.
In chemistry, it's often used as a precursor for things like pharmaceuticals, dyes or plastics.
I have synthesized benzaldehyde a couple times in the past, but the method in this video is, by far, the easiest way to get benzaldehyde.
Instead of making benzaldehyde, which is often lengthy and not very efficient, we just need to buy bitter almond oil.
The essential oil of bitter almonds is almost pure benzaldehyde.
Depending on the source, the essential oil can sometimes be used directly in synthesis without any prior purification.
To be safe though, it's always best to purify the oil, and that's what I'll be doing in this video.
This method saves a lot of time and doesn't cost too much, but a major downside is that it might be really hard to get the oil, depending on where you live.
I know that at least in the U.S. (United States of America), it's illegal to import bitter almond oil.
This law's in place for pretty much the exact reason why we want it.
Because it's pretty much just pure benzaldehyde.
Although I only used benzaldehyde legally, some people do use it as a drug precursor.
Here, I have some bitter almond oil that I got from eBay for about forty dollars.
Although the bottle does contain a hundred milliliters (100 mL), I'm only gonna be using seventy (70 mL) for this video.
I got it from eBay because this was the easiest source for me, but it doesn't really matter where you get it from. You just want it to be as pure as possible.
Benzaldehyde reacts quite readily with oxygen in the air to form benzoic acid (IUPAC: Benzenecarboxylic acid).
Almost all samples of benzaldehyde are contaminated with at least a little bit of benzoic acid, regardless of the source, whether you got it from a chemical company or as an essential oil.
To start things off, I add the bitter almond oil to a separatory funnel.
I then added in about forty milliliters of saturated sodium bicarbonate solution (40 mL saturated NaHCO₃)
Water and benzaldehyde don't really mix together and they stay separated as two distinct layers.
The separatory funnel is capped, shaken and then placed back on the stand for the layers to separate.
By mixing the benzaldehyde with saturated sodium bicarbonate solution, what we're trying to do is neutralize any benzoic acid that might be present.
The sodium bicarbonate will react with benzoic acid to form sodium benzoate, which will dissolve into the water layer.
After sitting around for a little while, the layers will eventually separate. The separation probably won't be exceptional, though, and each layer each layer might remain a little bit cloudy.
Into a beaker, I then drain off the lower water layer.
The upper benzaldehyde layer is drained into a small Erlenmeyer flask.
The benzaldehyde is a little bit cloudy due to the presence of water, so to dry things up I add some anhydrous magnesium sulfate (MgSO₄).
The magnesium sulfate will form a complex with the water and by doing so, it will dry the benzaldehyde.
The magnesium sulfate is then separated from the benzaldehyde by filtering it through a little bit of cotton.
What filters through is some nice, crystal clear benzaldehyde, which indicates that pretty much all of the water has been removed.
After everything is filtered through, the funnel is removed and I seal the flask using a stopper.
The next thing that I need to do is a vacuum distillation, but I wanna limit its exposure to air while I set things up.
After I've set everything up, this is what the final apparatus looks like.
In the flask on the left, we have the bitter almond oil; and in the flask on the right (that you can't really see) is where we're gonna collect our [distillate].
The extremely small red piece that you can see at the bottom right corner is the hosing that leads to my vacuum pump.
Also, all of the joints have been thoroughly greased to make sure that there's no leaks when I go ahead and pull the vacuum.
When we're ready to get things going, I lower the flask into the heating mantle and I turn on the stirring.
I then turn on my vacuum pump, and not too long after, the benzaldehyde starts to bubble a little bit.
At this point, everything's still at room temperature and there's no heating, so the bubbles coming off are either gas was dissolved into the benzaldehyde...
Or some low-boiling point solvents.
In any case, whatever came off just went right through the system and nothing collected in the receiving flask.
Once the system is under maximum vacuum, I go ahead and turn on the heating.
Not too long after, we start to get some distillate coming over.
The stuff that came over initially wasn't actually benzaldehyde, and it was mostly just water.
Unfortunately, at this time I didn't have a cow adapter, so I couldn't easily swap the receiving flasks.
In some cases, it is possible to re-pressurize the system, swap the flasks, re-pull the vacuum and continue the distillation, but with benzaldehyde this really isn't an option.
If we remove the vacuum and expose the system to air, we're gonna get a lot of benzoic acid forming.
I honestly tried to get away with doing it in a previous run, but let me just say, it does not work.
I ended up introducing a whole bunch of benzoic acid into my final distillate...
And this defeats the entire purpose of the whole cleaning procedure.
Luckily for me, the only thing that came over before the benzaldehyde was a little bit of water.
To get rid of the water, I just need to use a little bit of drying agent on the final distillate.
If however, the contaminant was something else than water and the amount was significant, I would say that a cow adapter is pretty much mandatory.
Anyway, we keep the distillation going until there's only a very small amount left in the distillation flask.
What we're left with a small amount of yellow residue that crystallizes upon cooling.
In our receiving flask, we have some nice, crystal clear benzaldehyde.
I turn off the vacuum pump, re-pressurize the system and I seal the receiving flask with a stopper.
When I'm ready to process the benzaldehyde, I remove the stopper and I clean the ground glass joint with a little bit of paper towel.
The joint is still covered with vacuum grease, and while it's probably okay to pour the benzaldehyde out over it, I like to clean it first.
Once I'm done cleaning away the grease, I add in some anhydrous magnesium sulfate.
I normally don't really like adding drying agents after a distillation, but in this case I kind of have to.
If I had a cow adapter at the time, and I was able to separate the initial distillate that came over, I wouldn't have to do this step.
Anyway, like before, the magnesium sulfate is separate from the benzaldehyde by just filtering it through some cotton.
This time though, instead of filtering it into a round bottom flask, I'm filtering it directly into the bottle that I'm going to be storing it in.
It does take a little bit of time to filter through, so to limit it's exposure to air, I just put a piece of paper on top of the funnel.
The final yield of benzaldehyde was about sixty-five milliliters (65 mL), which is very close to the seventy milliliters (70 mL) that we started with.
The bitter almond oil that we started with was nearly pure benzaldehyde anyway, and we were mostly just getting rid of water and some benzoic acid that might be present.
Most of the loss here pretty much just comes from the transfer steps.
I didn't want to have to use any solvents, so anything that was stuck on the sides of the flasks or in drying agent just ended up being lost.
I used the benzaldehyde from this video to make something called trans-cinnamic acid (IUPAC: trans-(2E)-3-Phenylprop-2-enoic acid)...
and the video for that will be posted after this one.
Trans-cinnamic acid is mostly used in the flavoring and perfume industry, but I want to use it to make styrene (IUPAC: Ethenylbenzene) and polystyrene (IUPAC: Poly(1-phenylethene)).
As usual, I'd like to thank everybody who's supporting me on Patreon.
Everyone who supports me with five dollars or more per video will get their name at the end like you see here.
I've been saying forever that I would introduce some more rewards and, you know, spice up my Patreon page a bit, but I kinda don't really have any ideas.
If you guys have any ideas as to what might be feasible and good tier rewards, please let me know in the comments.
Also, I'm trying to merchandise a little bit. I'm gonna be making some NileRed branded beakers, as well as lab coats.
If you think this is a cool idea, let me know in the comments and maybe leave some suggestions as to how I could design things or, you know, make it special or better in some way.
Anyway, these are the videos that I've already filmed and the ones that I plan to film. If you guys have any extra suggestions, please let me know.