Sciencemadness Discussion Board

Making Benzene by Decarboxylation Video

thors.lab - 23-7-2019 at 00:47

Hi,

I made a video on my new YouTube channel on making benzene by the thermal decarboxylation of sodium benzoate. I would love some feedback on my presentation and procedure. The procedure was based on NileRed's video on the same topic (with slight modification), as well as the stickied post on this board.

The link to the video is in my signature. I can't post it here, otherwise I will get IP banned by the filter (long story).

Equipment

For this procedure, I made a dry distillation flask that could withstand the high heat needed. I simply JB welded a 6" pipe to a quart sized paint can with a couple adapters so I could take the apparatus apart. I used a lot of steel JB weld which stood up to the benzene fumes perfectly. I then filed down the inside of the 6" pipe so that it would fit my 24/40 glass still head adapter.

To heat, I used a camping propane burner. For distillation, I used a 200mm Liebig condenser.

Summary of Procedure

1. 100g Sodium Benzoate and 60g NaOH were ground finely and mixed in a blender.

2. The powder was put into the paint-can apparatus, and I set up for simple distillation.

3. After 30 mins, white vapor came over and was collected as an orange liquid. Distillate was collected between 60ºC and 140ºC.

4. Orange distillate was washed with 2x 50mL dH2O. Waste water was stored for proper disposal.

5. I set up for simple distillation again.

6. Distillate started being collected in a fore-run beaker at about 74ºC. Then the temperature slowly climbed to 78ºC, where it halted. I initially thought this was still forerun, so I kept collecting it in the beaker.

7. Then I realized my solution was still wet, so the 78ºC was just an azeotrope. So I switched to a collecting flask.

8. When the distillation terminated, I crudely washed out the boiling flask and put the "fore-run" back in for re-distillation. This time, I collected anything above 77ºC.

9. The distillate was cloudy, and was dried with anhydrous MgSO4 for an hour.

10. The benzene was filtered through cotton. The result was crystal clear benzene.

Results

I collected 31mL of benzene, which weighed about 26.9g. This corresponds well with the density of benzene, and the disparity could be easily explained by my cheap scale and mechanical loss in the graduated cylinder. I'm fairly confident that this is close to 100% benzene.

The yield was 50%, which is good considering the yields of 45%-60% reported on the benzene thread. After the dry distillation, I noticed white powder still remaining, so I believe I could have improved my yield by continuing that initial distillation a bit longer.

Considering the price of my reagents, I calculated that this benzene has a marginal cost of about 11¢ per gram. This is not including the set-up cost (since it's a marginal cost), nor propane/electricity (I believe that would be a trivial cost), nor time (since this is a hobby, and I enjoy doing it anyway). The calculations are more thoroughly shown on my YouTube video.


I would greatly appreciate feedback on my video, whether it be about presentation, procedure, or safety.

Thanks,

Thor

Herr Haber - 23-7-2019 at 03:00

Good video, all the bits and pieces are there (safety, reagents, hardware etc.). You have a good voice (speed, no accent) and obvious editing skills.

The one big difference between your videos and similar ones is the cost analysis. I love details :)

thors.lab - 23-7-2019 at 11:59

Quote: Originally posted by Herr Haber  
Good video, all the bits and pieces are there (safety, reagents, hardware etc.). You have a good voice (speed, no accent) and obvious editing skills.

The one big difference between your videos and similar ones is the cost analysis. I love details :)


Thank you! I’m trying to improve the smoothness of my presentation. Reading off a word-by-word script makes me sound too mechanical, but no script and I can’t get a take without a mistake. I might try doing like an outline of keywords next time.

I think cost analysis is pretty important since it’s a big factor in determining whether to buy a reagent or make it. I also want to try to stick to very OTC-friendly pathways because I hate seeing a cool procedure and then realizing “wait — that chemical is impossible for me to get!”

morganbw - 23-7-2019 at 17:42

I enjoyed the video.

Amos - 24-7-2019 at 06:18

My two attempts at this yielded between 70% and 80% after re-distilling. I bathed an entire solvent can containing my reactants in open flame and simply attached and sealed a copper tube to a hole drilled in the lid. Leading the tube down a wide condenser into your receiving flask saves your glassware from the full onslaught of superheated vapor, which was extremely rapid. If you need more benzene in the future you might take advantage of that strategy. Your video is nice and professional though, well done. Have a sub on me :)

[Edited on 7-24-2019 by Amos]

thors.lab - 24-7-2019 at 07:35

Quote: Originally posted by Amos  
My two attempts at this yielded between 70% and 80% after re-distilling. I bathed an entire solvent can containing my reactants in open flame and simply attached and sealed a copper tube to a hole drilled in the lid. Leading the tube down a wide condenser into your receiving flask saves your glassware from the full onslaught of superheated vapor, which was extremely rapid. If you need more benzene in the future you might take advantage of that strategy. Your video is nice and professional though, well done. Have a sub on me :)

[Edited on 7-24-2019 by Amos]


Thanks! I’ll definitely keep that in mind for next time.

unionised - 24-7-2019 at 07:57

Quote: Originally posted by Herr Haber  
... no accent ...


LOL, that's a pretty clear American accent.

RedDwarf - 24-7-2019 at 09:57

Good video, liked the pace and clarity and I'm also a fan of the economics being included. Do you have a clear idea of what temperature you were achieving in the can over the course of the reaction?

PS. For an American the accent wasn't too atrocious :)

Tsjerk - 24-7-2019 at 10:03

Nice video! The fact you have a particular accent is helpful as, at least for me, it is easily understandable ;)

I most like the discussion on the mechanism at the end. In the beginning I disliked the explanation about the OTC level of the chemicals, as I think anyone wanting to make benzene will know about this... but that is something easily overlooked when the rest of the video is (very) good.

Nice result, I think you good get better even yields when you slowly but steadily raise the temperature while having a solid insulation up to the distillation head. I guess refluxing benzene and side-products back to the reaction medium doesn't do well for the yield.

Edit: you get bonus points for the chicken illustration during the washing step! I'm a biologist ;)

[Edited on 24-7-2019 by Tsjerk]

thors.lab - 24-7-2019 at 10:59

Quote: Originally posted by Tsjerk  

In the beginning I disliked the explanation about the OTC level of the chemicals, as I think anyone wanting to make benzene will know about this...
[Edited on 24-7-2019 by Tsjerk]


I think you're right about this. It definitely felt weird saying "I got sodium hydroxide at the hardware store…" I will keep that in mind next time!

thors.lab - 24-7-2019 at 11:03

Quote: Originally posted by RedDwarf  

Do you have a clear idea of what temperature you were achieving in the can over the course of the reaction?
PS. For an American the accent wasn't too atrocious :)


Quote: Originally posted by Tsjerk  

I think you good get better even yields when you slowly but steadily raise the temperature while having a solid insulation up to the distillation head.


I had a really hard time controlling the temperature with the propane burner. I couldn't even see the propane flame since it was light out. I started off too low, and nothing happened. Then I heated too much, and the rate picked up too much and some vapor was making it past. Then I kind of repeated this cycle a bunch of times until I found the sweet spot. With better temperature control I probably could have improved the yields a bit.

Because of this, I collected distillate from 60º to 140ºC, with the temperature fluctuating up and down quite a bit. I think I may have even turned off the propane altogether at once point and only noticed because I didn't see the heat waves from the flame...

Tsjerk - 24-7-2019 at 11:38

I'm thinking about getting a heating mantle with magnetic stirring for some time now... I have just being cheap until now.

Ubya - 24-7-2019 at 16:55

finally some quality chemistry videos, we have nilered, nurdrage and chemplayer, but all the smaller channels don't put enough effort, in my opinion most of them are just a video version of a lab note. very well made sir

(i also wanted to make chem videos but my location is sub optimal, and i have an accent, as herr haber pointed out it could be annoying)

thors.lab - 24-7-2019 at 18:11

Quote: Originally posted by Tsjerk  
I'm thinking about getting a heating mantle with magnetic stirring for some time now... I have just being cheap until now.


I got my hot plate on a killer deal. This guy was selling his hot plate on offerup for just $100, and I talked him down to $70. After meeting him, he threw in a ton of glassware too. I think he told me he was using it to make DMT lol... Got 2 KIMAX grad cylinders, a couple erlenmeyers, a weird RBF, and my hot plate (which was brand friggen new) all for $70. It was awesome.

thors.lab - 24-7-2019 at 19:10

Quote: Originally posted by Ubya  
finally some quality chemistry videos, we have nilered, nurdrage and chemplayer, but all the smaller channels don't put enough effort, in my opinion most of them are just a video version of a lab note. very well made sir

(i also wanted to make chem videos but my location is sub optimal, and i have an accent, as herr haber pointed out it could be annoying)


Thank you! You should give it a shot, you could always do a voiceover like ChemPlayer does. I was considering doing that in case I ever wanted to make something that was in a legal grey area like ChemPlayer does. But I opted to just try to avoid those things and use my real voice.

I would suggest a slightly better text-to-speech than chemplayer though

draculic acid69 - 25-7-2019 at 01:54



I got my hot plate on a killer deal. This guy was selling his hot plate on offerup for just $100, and I talked him down to $70. After meeting him, he threw in a ton of glassware too. I think he told me he was using it to make DMT lol...


Did you at least ask if he had any of this DMT still lying around???
Well worth the trip if you catch my drift.

chemplayer... - 26-7-2019 at 19:36

Nice videos - really well done! Looking forward to enjoying more...

Keras - 27-7-2019 at 05:17

I don't think the accent is that overwhelming. Not much different from NileRed's.

I'm not fun. I just bought a litre of benzene. :p

VSEPR_VOID - 27-7-2019 at 13:29

Good audio quality. You might also consider using a video style that involves always having something moving on screen to keep the attention of your audience. Notice how in a NurdRage or NileRed video they are always showing either a time lapse or something being handled.

Be careful with the benzene. It is difficult to communicate just how dangerous it is. If you can smell it you are being exposed.

thors.lab - 27-7-2019 at 15:52

Quote: Originally posted by chemplayer...  
Nice videos - really well done! Looking forward to enjoying more...


Thank you! I absolutely love your videos, one of my favorite channels!

thors.lab - 27-7-2019 at 15:54

Quote: Originally posted by VSEPR_VOID  
Good audio quality. You might also consider using a video style that involves always having something moving on screen to keep the attention of your audience. Notice how in a NurdRage or NileRed video they are always showing either a time lapse or something being handled.

Be careful with the benzene. It is difficult to communicate just how dangerous it is. If you can smell it you are being exposed.


Yeah I’ve been working on that. I might try writing an outline of the script BEFORE next time, that way I know roughly what I’m going to spend time talking about and what I need more footage for.

Thanks!