Benzaldehyde Preparation Using Nitric Acid

In this video I prepare benzaldehyde with a yield of 72% by the oxidation of benzyl alcohol with nitric acid. The product can be vacuum distilled to remove the red color and purify further, I didn't do this because the impurity won't interfere with my next reaction and that product will be distilled.
Where I found out about this method: www.sciencemadness.org/talk/vi...

[@vabbe71]

Very simple and smooth synth, great video clip

[@minusstage3]

Wow so much easier than retro-aldo of cinnamon essential oil! Thank you!

[@psycronizer]

Yeah, the method provides data on the various effects of parameters changes in graph form, and is very informative. The authors make no mention of the typical reaction byproducts when using this or similar methods, such as benzoic acid, benzyl benzoate, benzoin etc. One interesting part in the data suggests that due to the slow rate of the reaction kinetics, there is actually nothing to be gained by rapid stirring beyond 41 or so rpm !. So I'm just a little curious if the method was followed verbatim if that might cut down on oxidation byproducts due to less exposure to atmospheric oxygen, temp range for reaction in the paper is from 70 to 90 Celsius.

[@AlanCartman]

Great video. Is it possble to recover the unreactive HNO3?

[@user-oj5yj8tf9e]

Хорошо получилось, спасибо!

[@gabriellay2022]

thank u for very informative lesson

[@gabriellay2022]

Top notch. Teacher !!!!!!

[@bullwinklethemooseME]

Hello! Can I use an Graham condenser? Thanks

[@uxleumas]

Does benzyl alcohol react with the nitrous acid to produce the nitrite ester to any appreciable extend in the conditions shown in the video?

[@tracnemaker123]

So, the nitrite ion is capeable of oxidizing the benzyl alcohol? Is it due to standardpotential differences? Why NaNO2? Is the NO2 the reactant or...?

[@chemistryscuriosities]

Well done Tom.

[@TomsLab]

Thanks Canna, this was one of my favorites. Such a useful chemical with such a simple synthesis.

[@user-oj5yj8tf9e]

Грамотно!Спасибо;)

[@jbsc6180]

GREAT VIDEO

[@psycronizer]

so, Tom, after you did your vac distillation, what did you get ? I'm curious what you did about the obvious benzyl alcohol that would also be in it?...I know there is a marked difference in boiling points, with the alcohol being higher

[@jbsc6180]

psycronizer……………..you make a bisulfite adduct with the benzaldehyde and sodium bisulfite and then filter the adduct out as a solid. Then mix adduct with a base like sodium carbonate and break the adduct apart and back into benzaldehyde. Now the only liquids are benzaldehyde and water. Distill to get water out and dry with some molecular sieves

[@jbsc6180]

I wander what would happen if you used a NON BENZYL primary alcohol or a secondary alcohol?????????????????????

[@festerwalter]

hi, I would like to know, concentred nitric acid, ? %

[@CaptainBlackSea]

Thank you

[@00gsgvfhryeyw]

Great!

[@alllove1754]

Not bad at all! Now you can make some really nice soap, or desserts❤

[@Ambient_Scenes]

Cool video! Would this reaction also work with indole-3-carbinol instead of benzyl alcohol? I guess one problem is that indole-3-carbinol isn't very soluble in H20, but it is soluble in DMSO. However, the good thing is that the desired end-product, indole-3-carboxaldehyde is not soluble in water.

[@psycronizer]

That's actually a good question, the reaction might work, but, the alcohol group isn't the only thing that will get attacked by the nitronium ion, the hydrogen on the nitrogen will also be attacked, probably resulting in a nitro oxide being produced, no more amine there ! another issue might also be a side reaction between the aldehyde and the amine of different molecules condensing under those conditions...you might get SOME product, but, unless you optimize the reaction, track it, check for by products , then lol, no, this isn't a method you can use to get to your beloved tryptamine or whatever. You need to find another more suitable starting compound, they are out there..

[@Ambient_Scenes]

@@psycronizer I now tried this in a cou0le of different ways, but as you suspected the indole alsways reacts with itself. In fact, even just heating disolved indole-3-carbinol above about 50C makes it react with itself. It's an extremely finicky reaction, maybe the only way to do it practically is to protect the nitrogen first. Or just synthesise the aldehyde from indole itself using POCl3 in DMF.

[@psycronizer]

@@Ambient_Scenes well, if you bite the bullet and tell me what you are aiming for, maybe I can help. I actually have been having a bit of a nosey at trying to make 4 acetoxy indole, or anything that ends up with indole with a hydroxyl at the four position, ha. But it doesn't seem amenable to DIY amatuer chemsitry. Regarding your desire to get an aldehyde on the 3 position, yeah that would be great for reacting with something like, say, nitromethane followed by reduction, but even with nothing there at the 3 position, that is the most reactive point for substitution, oxalyl chloride will get an ethyl side chain on there...

[@zipcoszipcos655]

Can I use Nitric Acid 90-99% in a volume of 13.1ml? Will productivity increase?

[@blakraven7895]

what is this used for ???

[@johnblacksuperchemist2556]

GREAT VIDEO .....I tried a nitric acid oxidation of mixed xylenes to make toluic acid but i only got like a 25% yield.

[@psycronizer]

that's O.K. enough to be considered a success in any org. chemist's book.

[@johnblacksuperchemist2556]

@@psycronizer ........Yeah i guess your right. It was a LONG and nasty experiment though. I did learn some stuff though.

[@midwestchem368]

I think I've read p cymene would be the best starting material to make p toluic acid. As I wanted to do the same recently but just never got around to it. Seems I do that alot though lol.

[@shonkysidewayssam6134]

Awesome stuff. I hope that is a home lab set up. Good taste if so... ;-)

[@TomsLab]

Yep, this is my home lab.

[@AussieChemist]

Do you do post voice recording or live ?

[@TomsLab]

All of the speaking was live in the lab, that's why there is constant background noise of my fume hood.

[@AussieChemist]

Tom's Lab it does save a lot of time by doing live recording, but the fume hood noise does seem to be a problem. I like the fumehoods in universities where the fans are installed somewhere else far away and connected by tubes it’s truely noises free

[@chadkline4268]

Can be made in large amounts via toluene, using electricity and a manganese III oxide catalyst.

[@raymondmoody2516]

care to elaborate further?

[@chadkline4268]

It is an old industrial process for making benzaldehyde that gives high yields of product, and produces next to no waste to be disposed of. This process uses the electrode-generated reagent, Mn+3, to oxidize toluene to benzaldehyde in very high yield with very few byproducts. The Mn+ 3 is electrically made from the easily available Mn+ 2 salts. During the reaction, the Mn+3 is reduced to Mn+2, which can be returned to the process and used over and over again just by electrically oxidizing it again to Mn+3. This method is taken from US Patent 808,095, which dates to 1905.

[@chadkline4268]

After two to three hours the reaction is completed and the solution and the undissolved salt have become perfectly clear. The oily mixture is driven out with steam and worked up in the known manner. The manganese mixture goes back for repeated electrolysis. From the oily mixture about 0.6 kilo of toluene are recovered and about 3.7 kilos of benzaldehyde are obtained, which is over eighty per cent. of the theoretical quantity in relation to the toluene consumed. No benzoic acid is produced by this method of working, but only small quantities of condensation products in addition to the benzaldehyde. If, however, a considerablyv more diluted acid is employed, benzoic acid will be formed besides the aldehyde. A stronger acid leads to an increased quantity of condensation products, but accelerates the reaction. If the sulfuric acid is considerably stronger than seventy per cent, the electrolytic oxidation does not take place. If it is too dilute, pyrolusite and permanganic acid are produced at the same time. Similar effects are produced if instead of toluene its higher homologues are employed, and many substituted toluenes behave in the same manner. Isoeugenol is oxidized to vanillin.

[@ScienceWithJames]

Where did you get your hot plate/stirrer?

[@TomsLab]

It's a Corning PC-351, I got it from eBay for ~$120. Ones in good condition can range from $100-200.

[@samcat4005]

where'd you get the benzyl alcohol?

[@TomsLab]

I got mine from Amazon, although you can find it from other online stores.

[@georgebritten8208]

Would this reaction work with piperonyl alcohol?

[@waspstomper6250]

The methylene-dioxy group is sensitive to strong acids. Whenever I do strongly acidic reactions on Anything with a methylenedioxy group, I always get goop or polymerized tar. Using dilute HCl during the pinacol rearrangement in the synthesis of MDP2P, however, it seems to be dilute enough to not ruin the precursor. Besides, if you want MDA just go buy some helional, then react with hydroxylamine and carbonate to get the oxime, then reflux that in xylene with sodium acetate at 130C for 8 hours to get the amide, then do a Hoffman rearrangement to get MDA.

[@lorddesigner9121]

Thenk you so much

[@gerrehrthertfth8194]

I dont understand... Isnt the benzaldehyde forming benzoic acid on contact with air? Shouldnt you do something to prevent it from happening?

[@TomsLab]

It would oxidize (especially when hot), but the reaction continuously produces N2O as well as NO, which keep oxygen out for as long as the reaction is happening.

[@tmfan3888]

HNO3, dichromate, which is better?

[@TomsLab]

I would say HNO3, mostly because it is not carcinogenic, also there is less chance of over oxidation and (at least for me) it is cheaper and easier to obtain/make.

[@zodd0001]

It is a bit impure, benzaldehyde is colorless although it get easily yellowish upon air exposure.

[@eskee1]

Question, Your familiar with benzaldahyde and how it works?

[@zodd0001]

@@eskee1 yes

[@htomerif]

Why is everyone's benzaldehyde brown or red? Its supposed to be colorless.

[@cawa3862]

Why do we need NaNO2 and what is the literature source of this reaction ?

[@TomsLab]

NaNO2 is protonated to give HNO2, which reacts with BnOH, making benzyl nitrite. The nitrite ester decomposes, yielding BzH and HNO. The latter then reacts with HNO3 making more nitrous acid, and the process starts over. From the paper Kinetics of Oxidation of Benzyl Alcohol with Dilute Nitric Acid, published in 2005 (easy enough to find by googling). I got the PDF from a thread on ScienceMadness.

[@jbsc6180]

@@TomsLab …………...I was wandering the same thing. I really do not understand nitric acid/nitrous acid type oxidations. Great answer but I got a question. Is BzH short for benzaldehyde???? Never seen that before

[@cvspvr]

@@jbsc6180 yes. BzH is benzaldehyde. Bz is the benzoyl group which is C6H5C(O)?

[@jbsc6180]

@@cvspvr ……..Wow that was like a year old post. Thank you VERY much for the reply. Is there any word a chemist will not try to abbreviate...lol.

[@SunriseLAW]

@@jbsc6180 lol ?

[@cawa3862]

Benzaldehyde should be colorless

[@TomsLab]

Yes it should be. The red color comes from a minor impurity. Not sure what it is exactly, but I removed it by vacuum distillation a few weeks ago.

[@ahmetselcuk1400]

Piperic acid oxidation piperonal ...please ..parmangamate no aldehyde

[@user-tm5dn7od3y]

Нитрит натрия лишний,и без него нормально

[@firehoax9230]

Tom's bab