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Author: Subject: The Synthesis of Benzoyl Chloride via The Sulfur Catalyzed Chlorination of Benzaldehyde
Johnny Windchimes
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smile.gif posted on 31-8-2020 at 18:29
The Synthesis of Benzoyl Chloride via The Sulfur Catalyzed Chlorination of Benzaldehyde


Good day all,

I have not had occasion to do any meaningful chemistry as of late, but I will post one of my more successful reactions circa January 2020.

Just from my own notes, extrapolated and explained a bit of course.

Few things before we touch off:

1. Benzaldehyde was purchased (not illegal where I am) from eBay, but it could've easily been made. I used up my home-made and vac distilled batch I made via Praxyis(sp) aka Doug from Dougs Lab & Tom from Tom's Lab thread on the Nitric acid oxidation of Benzyl Alcohol to Benzaldehyde doing test runs that failed, but in my opinion the failures had nothing to do with the quality of the benzaldehyde, just my poor temperature control.

http://www.sciencemadness.org/talk/viewthread.php?tid=72076


2. Chlorine was made from the TCCA and HCl dripped method, re: Nurdrage and many others here; I used a 2 molar excess but would use a bit more (2.25 - 2.5 mol excess) in the future as not all reacts even with heating and stirring.

https://www.youtube.com/watch?v=hLHfN7GvAyI


3. I used ordinary garden Sulfur as the catalyst, recrystallized from toluene so it was a shiny, sparkly pure yellow (what a waste of time but I didn't have another source and I wasn't waiting weeks for eBay).


4. You need a hood, great ventilation or a good 550 CFM fan and 6 inch tubing like I had with my temporary setup to suck out not only unreacted chlorine, but the HCl gas this generates. It fumes in air, damp night air much more vividly, for the neighbour conscious among us.

I use a 3M mask with Acid cartridges the entire time I do anything like this as backup, but it WILL NOT stop anything but blow-by or nuisance chlorine vapours so be warned. The chlorine generator, once started, can't be stopped easily in my experience.


Ok, onto the preamble:



Introduction
-----------------

Benzoyl Chloride was Synthesized via the Sulfur Catalyzed Reaction of Chlorine upon Benzaldehyde at Moderate Temperatures.

Read the attached MSDS for Benzoyl Chloride before diving into this one, as it can be pretty toxic and fumes in open air. It's also very lacrimatory. Spill some on a hot stove or hotplate? Bam you just made PHOSGENE gas.... Be warned!

US Patent 3894923 (Attached below), was used (but kind of not used) as a guide.

What I mean by this is their patent is all about UV light helping the chlorination along, but they give a comparative example at the very bottom using plain old Sulfur.


Materials & Reagents
--------------------------

312 grams TCCA (Tri-Chlorocyanuric Acid)
500 ml 31.45% Hydrochloric Acid
212 grams Benzaldehyde
0.5 grams Sulfur
CaCl2 for drying tube(s)

Hotplate
Stirbar
Silicone Tubing
1 x 2000 ml 3-neck flat bottom flask
1 x 500 ml 3-neck flat bottom flask
4 x screw-down type thermometer adapters (3 minimum)
1 x 500 ml pressure equalized dripping funnel (or smaller one and be able to add more to it as you go, which is bloody TERRIBLE with a reactor under pressure making Chlorine)
1 x drying tube
1 x reflux condenser
1 x small aquarium air pump (optional but recommended)
1 x wicked ventilation system or fume hood


Experimental
------------------

To a 3-neck, 500 ml flat bottomed flask was added 2 moles of Benzaldehyde (212 grams), 0.1% of this weight in elemental Sulfur (about 0.5 grams was used), and a small stir bar.

The flask was then placed on a hotplate, one neck affixed with a thermometer well attached to an electronic thermo-couple, the center neck attached to a reflux condenser, and the other side neck attached to a thermometer adapter that had a small hollow borosilicate glass tube running through it down into the stirred benzaldehyde for chlorination. To the top of the reflux condenser was attached a drying tube packed with CaCl2, to prevent water condensing down into the reaction flask.

The aforementioned glass tube was attached via silicone fish tank style tubing to the chlorine generator, which will now be described:

A 2000 ml flat bottom 3-neck flask was filled with 312 grams of powdered TCCA, the center neck rigged with a 500 ml pressure equalized dripping funnel. The dripping funnel was filled with a slight molar excess of 31.45% Hydrochloric acid, approximately 500 ml (or about 160 grams of HCl) worth. More HCl can be added to make swirling this flask easier to ensure all the TCCA reacts.

One side neck of the above mentioned flask was fitted with a hollow 200 mm 24/29 borosilicate glass tube, packed with CaCl2 and cotton-balled at both ends. This is to ensure the generated chlorine gas is dry. This 200 mm packed drying tube was attached to yet another thermometer screw-down type adapter and silicone hosing to the reaction flask glass tube to provide the chlorine.

The other and final neck of the flask was fitted with a thermometer adapter, silicone tubing, and that tubing was attached to a VERY tiny aquarium style pump. This was to keep mild but consistent positive pressure in the chlorine generator to prevent suck-back issues. I tend to do this on every gas generator reaction I do, especially HCl gas generators, to avoid suck-back. As long as that drying tube is well packed with a suitable drying agent, it has always worked well.

The 500 ml pressure equalized dripping funnel was filled with 500 ml of 31.45% HCl, and the small aquarium air pump turned on to check the flow, bubble size and depth into the benzaldehyde from the chlorine generator (at this point it was all just regular room air).

Cold water was now run through the reflux condenser, and the hotplate and magnetic stirring was turned on and a temperature of approx (+/- 5 C) 120 Degrees C was reached. Ventilation was begun (ideally should be on before now as a rule).

The 500 ml HCl was now slowly at first dripped onto the TCCA powder. Immediately a yellow-green chlorine gas haze was seen in the chlorine generator flask, and chlorine was starting to be piped into the benzaldehyde.

The chlorine generator flask was lifted and swirled occasionally, and as the reaction continued the drip rate was adjusted to provide a steady (as can be) stream of gas into the reaction flask.

At approximately T + 10 minutes the reaction flask temperature was approximately 135 Degrees C, and the hotplate heating was turned off and passive air cooling was started. HCl gas was steadily evolving from the top of the reflux condenser, out the drying tube and being sucked out of the lab space. Litmus paper held above this drying tube turned bright red very quickly.

After approximately T + 1 hour the reaction flask cooled to the point where I stopped the cooling fan, but did not re-start the hotplate.

Around T + 1.5 hours the reaction was approximately 110 Degrees C and the hotplate was cautiously restarted. Litmus paper at the exit drying tube atop the reflux condenser was still bright red with HCl gas evolution.

Around T + 2.25 hours the chlorine generation began to slack considerably, and the flask was swirled. I placed in on a small pan and used a gas range to briefly heat the flask, but this was discontinued as it really was not doing much in the way of gas generation. Litmus paper at the exit drying tube atop the reflux condenser was still bright red with HCl gas evolution.

Around T + 2.5 hours, the entirety of the 500 ml HCl was finished dripping into the chlorine generator. Litmus paper at the exit drying tube atop the reflux condenser was still bright red with HCl gas evolution.

At T + 3 hours, the reaction flask was approaching 95 Degrees C, the entirety of the HCl was long since added, and litmus paper at the exit drying tube atop the reflux condenser was no longer instantly turning bright red, indicating the HCl gas evolution from the reaction was slowing and the reaction was close to completion.

At T + 3.25 hours, I turned off the hotplate, stirring, cooling water, and CAREFULLY disconnected the glass tube feeding the reaction flask with chlorine (aquarium air pump still on as to avoid any suck-back). I then quickly stoppered the reaction flask and turned off the aquarium air pump to avoid filling the room with even more HCL and Chlorine gas vapours. The Chlorine generator flask was quenched carefully with water several times and its contents disposed of.

The contents of the reaction flask were poured into a 250 ml round bottom, affixed with a vigereux column, and set up for vacuum distillation.

Everything was collected until there was a brown tar and what remained of the Sulfur catalyst in the distillation flask. In the collecting flask was 204.4 grams of a clear, slightly syrupy liquid that fumed upon exposure to air. Temperature was approx 210 - 220 Degrees C at the still-head when it was shut down.

This flask was then setup for fractional distillation at atmospheric pressure. Everything below 197 degrees was discarded (Benzoyl Chloride bp = 197.2 C), and 199.9 grams of clear, colourless liquid was collected. This liquid was slightly viscous and fumed upon exposure to air.

The temperature at collection was very sharp and steady, and the space between fractions very large. Inside the distillation flask was a small amount of a slightly yellowish clear fluid, which crystallized upon cooling. This was most likely benzoic acid from the atmospheric distillation of whatever remaining benzaldehyde came over during the vacuum distillation.

The Benzoyl Chloride was poured into a dark glass bottle and stored in the fridge. Depending on what you are using it for, some desiccant may be advisable for storage.

See attached paper, Cahiez 2001, for a broad overview on storage and handling.


Yield
--------

2 moles Benzaldehyde 212.28 grams = 2 moles Benzoyl Chloride 281.14 grams theoretical yield.

199.9 grams actual yield of Benzoyl Chloride / 281.14 grams theoretical yield = 71.1%

Ergo, the final molar yield was 71.1% on starting Benzaldehyde.


Comments
---------------

As mentioned, without risking di and/or tri-chlorinating the Benzaldehyde, a bit more chlorine could be used. This might get the yield up a bit.

The yield tracks decently from the example in the patent (Their yield was listed as 82%).

Overall I think this worked pretty damn well all things considered. Working with chlorine or any gas really always kind of sucks, especially in an amateur setting, so I feel this was a great success.

Questions, critiques and comments always welcome!

Cheers~!





Attachment: US3894923 - Sulfur Catalyzed Winner - Copy.pdf (119kB)
This file has been downloaded 44 times

Attachment: cv3p0112 - Benzoyl Chloride Purification Ref - Copy.pdf (313kB)
This file has been downloaded 35 times Purification of Benzoyl Chloride - Copy.png - 34kB

Attachment: BENZOYL-CHLORIDE MSDS - Copy.pdf (57kB)
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*EDIT: Typos, attachments, and flask sizes corrected*


Attachment: cahiez2001 - Benzoyl Chloride Facts - Copy.pdf (77kB)
This file has been downloaded 34 times

[Edited on 1-9-2020 by Johnny Windchimes]



[Edited on 2-9-2020 by Johnny Windchimes]




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[*] posted on 1-9-2020 at 05:13


Have you tried it without S2Cl2 or UV?



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[*] posted on 1-9-2020 at 05:22


Quote: Originally posted by S.C. Wack  
Have you tried it without S2Cl2 or UV?

The reaction works with just BzH + TCCA in CH2Cl2 as in e.g.:

http://doi.org/10.1002/adsc.201500912
http://doi.org/10.1021/acs.orglett.5b01579 (free Supporting Information)

Also reported to work with BnOH but may give some BzOBn.




[Edited on 04-20-1969 by clearly_not_atara]
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[*] posted on 1-9-2020 at 06:03


The reaction works with just chlorine i.e. neat.



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[*] posted on 1-9-2020 at 11:29


https://www.prepchem.com/synthesis-of-benzoyl-chloride/

See the second preparation

[Edited on 1-9-2020 by Tsjerk]
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shocked.gif posted on 1-9-2020 at 14:20


Quote: Originally posted by clearly_not_atara  
Quote: Originally posted by S.C. Wack  
Have you tried it without S2Cl2 or UV?

The reaction works with just BzH + TCCA in CH2Cl2 as in e.g.:

http://doi.org/10.1002/adsc.201500912
http://doi.org/10.1021/acs.orglett.5b01579 (free Supporting Information)

Also reported to work with BnOH but may give some BzOBn.


I should definitely mention, the TCCA DCM Benzaldehyde room temp reaction of which you speak....

I followed the paper precisely. Scaled it up big time of course. But guess what.... it's not that papers lie, it's that scaling doesn't always SCALE correctly....

5 days later (as per the paper, scaled up x like 100 if I recall as this wasn't even pretending to be preparatory), I distilled off the DCM, at atmospheric, and as I always wear my 3M Mask as a rule, my life was saved that day.

Last thing I recall was the still-head temp going to about 180 degrees C, and then BOOM.

Vigereux, 3-way, thermometer well, everything blew and it all hit the roof. 1-neck flask in the 2000 ml mantle didn't crack for god knows whatever reason. The entire lab space was filled with thick white smoke. The condenser was toast. THICK WHITE SMOKE.

I turned off the water, and bumble f*cked my way out of the lab space and up the stairs. White acrid smoke was clearly noticed (and tasted) through my respirator.

The entire house (thank god its all mine, and isolated-ish) was filled, via the furnace air fan, with this acrid white smoke.

THIS IS WHY YOU SHOULD NEVER DO CHEMISTRY LIKE THIS IN AN APARTMENT OR SHARED DWELLING.

All the windows were thrown open and whatever emergency ventilation I could muster was turned on. I was very sure I made the target compound before it blew, hence the white smoke, but couldn't be sure I didn't just make a pile of PHOSGENE GAS.

5 panic attacks later here I am, and all the wiser for it.

I still don't know what touched it off. Too much heat? Contams? Side products reacting? Bad JuJu?.....

I was very lucky, and tell this tale to remind everyone that however much you think you know (and oh I know so very little....), it's never enough to duck safety precautions.

Which I didn't, and never will. That's why I'm able to type these words this day.

I'll muster a picture or two I took an hour after..... If I can find them..... they make Magpie's "Oleum made UNCONTROLLABLE FUMES" post(s) pictures look like someone discreetly vaping in a movie theater compared to the toxic cloud of stupid I made that day....



*EDIT* No, never tried UV, or anything like S2Cl2, but was looking into all the literature I could find at the time, and do recall some preps along those lines.

[Edited on 1-9-2020 by Johnny Windchimes]

[Edited on 1-9-2020 by Johnny Windchimes]

[Edited on 1-9-2020 by Johnny Windchimes]

Attachment: KABOOM - gaspa2015 - Benzoyl Chloride via Benzaldehyde and TCCA - Copy.pdf (508kB)
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[*] posted on 1-9-2020 at 15:11


Quote: Originally posted by clearly_not_atara  
Quote: Originally posted by S.C. Wack  
Have you tried it without S2Cl2 or UV?

The reaction works with just BzH + TCCA in CH2Cl2 as in e.g.:

http://doi.org/10.1002/adsc.201500912
http://doi.org/10.1021/acs.orglett.5b01579 (free Supporting Information)

Also reported to work with BnOH but may give some BzOBn.



Post Script :

Your article's almost the same as mine..... Gaspa essentially posted it twice with minor albeit significant changes..... Even the wording is the same....

Wonder if your version KABOOMs too? I won't be trying it out to see....

Like, it's a carbon copy with chemicals sub'd in.... spooky actually....



Attachment: gaspa2016 - Copy.pdf (406kB)
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Attachment: KABOOM - gaspa2015 - Benzoyl Chloride via Benzaldehyde and TCCA - Copy.pdf (508kB)
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[Edited on 2-9-2020 by Johnny Windchimes]




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[*] posted on 1-9-2020 at 15:47


Well, the good news is you didn't make phosgene. You had already distilled off the DCM when the explosion occurred; if there was any phosgene, you'd be dead.

The bad news you already know. One key safety precaution: always start small!

Quote:
I still don't know what touched it off. Too much heat? Contams? Side products reacting? Bad JuJu?

TCCA itself is potentially unstable: the reaction C3O3N3Cl3 >> 3/2 Cl2 + 3/2 N2 + 3 CO is already exothermic with deltaH = -210 kJ/mol!

So it is not a good idea to heat mixtures containing TCCA, DCCA or MCCA. All three can decompose violently. The stated thermal decomposition temperature of TCCA is 225 C from the MSDS:

http://www.wisdah.com/imgs/2018/10/MATERIAL-SAFETY-DATA-SHEE...

With "catalytic crud" this could happen at 180. Since the BP of BzCl is 197 C I conclude that BzCl produced by this method can not be distilled safely at atmospheric pressure.

[Edited on 1-9-2020 by clearly_not_atara]




[Edited on 04-20-1969 by clearly_not_atara]
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[*] posted on 1-9-2020 at 16:10


Quote: Originally posted by Johnny Windchimes  
*EDIT* No, never tried UV, or anything like S2Cl2


Well, I'd think that would be the point of hot S + Cl, although the older directions call for cold no-S.




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[*] posted on 1-9-2020 at 17:51


Quote: Originally posted by clearly_not_atara  
Well, the good news is you didn't make phosgene. You had already distilled off the DCM when the explosion occurred; if there was any phosgene, you'd be dead.


Yes indeed. I wasn't intending on posting that 'failure', (if such a brush with the afterlife can be such ascribed to...), but when that Gaspa article was posted I felt hurriedly compelled to do so.

I am clearly not the best chemist, nor do I pretend to be, but I would certainly lose sleep knowing that if someone Googled 'Benzoyl Chloride', they would look and think, as I did, "boy this Gaspa article is way easier, if not a bit time consuming", and trod down that path as blindly as I did.

Again, it's not Gaspa's fault, it's mine, scaling up a procedure from millimoles to mole'y moles.....

Learn from this is all I ask, if anything at all....

[Edited on 2-9-2020 by Johnny Windchimes]




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[*] posted on 2-9-2020 at 06:01


Quote: Originally posted by S.C. Wack  
Quote: Originally posted by Johnny Windchimes  
*EDIT* No, never tried UV, or anything like S2Cl2


Well, I'd think that would be the point of hot S + Cl, although the older directions call for cold no-S.


If memory serves, I didn't try the UV initiated version(s) of this synthesis because my mercury vapour HID lamp, that I in no way had lying around from the old veg cycle of growing the devils lettuce, was pooched from me dropping it onto concrete....




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[*] posted on 2-9-2020 at 06:30


Well, it wouldn't have made sense to try the UV anyway because the reaction runs without a catalyst with nearly quantitative yield.
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[*] posted on 2-9-2020 at 12:02


Quote: Originally posted by Johnny Windchimes  
Quote: Originally posted by clearly_not_atara  
Well, the good news is you didn't make phosgene. You had already distilled off the DCM when the explosion occurred; if there was any phosgene, you'd be dead.


Yes indeed. I wasn't intending on posting that 'failure', (if such a brush with the afterlife can be such ascribed to...), but when that Gaspa article was posted I felt hurriedly compelled to do so.

As far as I can tell, nothing actually went wrong during the rxn procedure itself.

The other lesson is to learn about the reagents you use, even "normal" ones like TCCA. I doubt you would have tried a thermal distillation if you had known the decomposition temperature beforehand.

Gaspa's procedure is fine; heating TCCA to 200 C is not fine.

EDIT: I've been quite stupidly lazy here. I should have posted the actual procedure:

https://pubs.acs.org/doi/suppl/10.1021/acs.orglett.5b01579/s...

TCCA (55 mmol) was portionwise added over a period of 1-2 minutes into a solution of benzaldehyde (55 mmol) in 162.5 mL dichloromethane under Ar atmosphere and at room temperature. The resulting suspension was stirred at room temperature for 5 days under Ar (the reaction was monitored by TLC until disappearance of aldehyde). Aliquot was analysed with HPLC (CH3CN, flow rate 1 mL/min, Pressure 380 PSI, injection volume20 μL, t. R 3.899) and compared with the chromatogram of standard (benzoyl chloride obtained by commercial source). The mixture of reaction was filtered on Celite, then the solvent was removed under vacuum and the residue was distilled. 1H NMR (400 MHz, CDCl3) δ : 8.08 (d, J= 7.8 Hz, 2H), 7.66 (t, J= 7.4 Hz, 1H), 7.48 (t, J= 7.6 Hz, 2H).13C NMR (100 MHz, CDCl3) δ : 168.3, 135.4, 133.2, 131.4, 129.0.

But really I should also have known myself to warn about TCCA decomposition.

[Edited on 3-9-2020 by clearly_not_atara]




[Edited on 04-20-1969 by clearly_not_atara]
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[*] posted on 2-9-2020 at 19:07



Quote:

Again, it's not Gaspa's fault, it's mine, scaling up a procedure from millimoles to mole'y moles.....


Can't be overstated. For myriad reasons, not just the scaling.

Solubility in DCM aside, I should point out I did vac filter off the very insoluble unreacted TCCA / reaction mixture to be left with a crystal clear yellow liquid before distilling it.

Definitely helped it go down from ultra lethal hand grenade type explosion to just a garden variety horrifyingly scary accident I would wager....:o


@Tsjerk, I started experimenting with the simplest method(s) I could find, and could not for all my 'skill' get the catalyst free reaction(s) to run properly. 10.... 20 percent yields tops. Very frustrating at the time, so I looked into alternatives like Gaspa.

[Edited on 3-9-2020 by Johnny Windchimes]




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