Sciencemadness Discussion Board

Acetic Anhydride from Zinc Acetate?

Peaches - 4-2-2021 at 20:43

TL;DR: I may have made acetic anhydride without chlorinating agents or phosphorous compounds using accessible chemicals.

I found a paper that details how to make basic zinc acetate. While basic zinc acetate isn't a very interesting chemical, the reaction the authors used to make it was. In the reaction four molar equivalents of anhydrous zinc carboxylate are heated under vacuum to yield one molar equivalent of carboxylic acid anhydride and one molar equivalent of basic zinc acetate. At first, this sounds horribly inefficient, and it is... But I speculate that you can recycle the basic zinc acetate back into regular zinc acetate by acidifying it with acetic acid. You might be able to do several runs before having throw out the zinc acetate.

1) The acetic acid is formed 4 Zn(CO2CH3) ---> Zn4(CO2CH3)6O + (COCH3)2O
2) The zinc acetate is regenerated Zn4(CO2CH3)6O + 2 HCO2CH3 ---> 4 Zn(CO2CH3) + H2O

I decided to try this out for myself as synthesizing carboxylic acid anhydrides without chlorinating agents would be a very valuable reaction for myself and the amateur chemist community; So I set to work and made some zinc acetate crystals by refluxing zinc oxide with 2 molar equivalents of acetic acid. A little bit of water was also added to better solvate the reactants.

ZnO + 2 HCO2CH3 --->Zn(CO2CH3)2

After 3 hours of refluxing, the reactants were taken off heat and allowed to cool. The result can be seen in the first attached picture. The zinc acetate crystals were vacuum filtered and placed in a beaker. The beaker was heated to 150oC for 5 hours with regular agitation to dry them. The result was a fine, free-flowing, bone dry powder. For the next step, all involved equipment was rigorously dried before use. An Erlenmeyer flask was charged with anhydrous zinc acetate. A vacuum distillation apparatus was assembled around the flask. Do note that using a water aspirator is not advisable due to the moisture sensitive nature of this reaction. I used a shop vac and as you will soon read, this was a blunder too. In any case, I pulled a vacuum and warmed up my hotplate to 250oC. The reaction sputtered real bad. Some of the zinc acetate found its way up to the still head and some even into the receiving flask. The whole reaction was kinda sketch, and the sputtering kinda spooked me. The heat was held for 6 hours as was consistent with the paper, but no distillate came over. I was very upset at this point because I THOUGHT the reaction didn't work. I unplugged my hotplate, let everything cool, and proceeded to disassemble the apparatus. But when I took the stopper off of the still head, I was struck with the horrible stench of acetic acid. You know the smell. I concluded that I did make some acetic anhydride, but due to the high reaction temperatures, the acetic anhydride vapor was sucked up the vacuum line before it had a chance to condense. The vacuum I was using was 70 mcmHg, which I think was too much. Also the vacuum pump oil reeked of acetic acid; I really hope it didn't damage my pump.

So in conclusion I'm not sure if I made acetic anhydride or not... but based on the horrible pungent acetic acid like smell, I think I did. If someone else wants to verify that would be awesome!

Here is a link to the paper.

Attachment: Freshly prepared zinc acetate.HEIC (1.4MB)
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Attachment: Zinc acetate sputtering.HEIC (1.6MB)
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Attachment: Zinc acetate dust in reciving flask.HEIC (1.7MB)
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Fery - 5-2-2021 at 00:00

Hi Peaches and welcome to the forum!
Interesting. I thought that such acetate salts (Ca2+, Sr2+, Ba2+, Zn2+, Mn2+) produce acetone and metal carbonate on heating. But you used vacuum and temperature kept at 250 C on hotplate so maybe 200 C inside reaction flask to prevent that reaction.
What is 70 mcm Hg? Milli centimeter? I have 2-stage vacuum pump with granted vacuum 0,3 Pa and at full vacuum it usually decreases boiling point by approx. 150 C (it depends on the compound distilled, condition of the pump, freshness / purity of oil and oil vendor, quality of ground glass joints and quality of vacuum grease applied to the joints e.g. Korasilon is good etc).
For adjusting vacuum level you need a vacuum control valve, if the vacuum level is too high (low absolute pressure) you allow a little of air to be sucked through the valve. For trapping low boiling liquids you need to connect a cold trap between the distillation apparatus and the pump. This is a vessel surrounded by something very cold (dry ice + acetone, or for special purposes even liquid nitrogen) in which the vapor condenses and does not enter you vacuum pump.

Corrosive Joeseph - 5-2-2021 at 02:08

Quote:

Zinc(II)acetate dihydrate loses its water of crystallization at 100degreesC to give Zn(CH3COO)2

Heating Zn(CH3CO2)2 in a vacuum results in a loss of acetic anhydride, leaving a residue of basic zinc acetate, with the formula Zn4O(CH3CO2)6. This cluster compound has the tetrahedral structure shown below.



Koyama, H.; Saito, Y. (1954). "The Crystal Structure of Zinc Oxyacetate, Zn4O(CH3COO)6". Bull. Chem. Soc. Jpn. 27 (2): 112–114.
https://www.journal.csj.jp/doi/10.1246/bcsj.27.112
https://sci-hub.tw/10.1246/bcsj.27.112



/CJ


Zn4O(CH3CO2)6.PNG - 10kB

Corrosive Joeseph - 5-2-2021 at 02:11

This is most interesting to me and deserves further effort.
Just found two half asssed attempts here, one from 2talltman and another by aga.... Waffles seemed to think he had success with silver acetate but I guess it is expensive.

Link for anyone who's interested -
https://www.sciencemadness.org/whisper/viewthread.php?tid=9&...



/CJ

njl - 5-2-2021 at 07:04

On the acetic anhydride thread this concept has been brought up a couple times and each time it gets shot down (justifiably). It's interesting to see experimentation with this method. Good stuff :)

pip - 5-2-2021 at 14:46

Here’s some important information, it seems that it needs to be done at a max of 250c and without the presence of oxygen according to

https://opus.lib.uts.edu.au/bitstream/10453/20439/2/02Whole....

Basic zinc acetate was never the coproduct, the coproduct is zinc oxide, a side reaction which is where the failure comes from, you’re going after the wrong reaction.

[Edited on 5-2-2021 by pip]

[Edited on 5-2-2021 by pip]

pip - 5-2-2021 at 15:16

If I cared enough to try I’d try 200c with an inert atmosphere and no vacuum.

But ketene seems easier, for now at least. It’s predictable.

Boffis - 6-2-2021 at 04:02

Interesting work Peaches! Didn't you use a condenser/receiver beyond the stillhead? I am surprised that the acetic vapours were carried away if you were. If acetic anhydride was formed but remained in the flask I wonder if you could extract it was a non-aqueous solvent such as pet. ether?

clearly_not_atara - 6-2-2021 at 08:29

The reason that most of us don't believe the zinc acetate paper is because their finding of acetic anhydride was based on a spectroscopic analysis (EDIT: it was byok3y critiquing the NMR) which some more knowledgable members pointed out was equally consistent with a mixture of acetic acid and acetone:

http://www.sciencemadness.org/talk/viewthread.php?tid=9&...

Also, the requirement of extremely stringent oxygen and moisture-free conditions makes it more technically demanding than it initially sounds. The similar method with silver acetate is known to work in up to 70% yields, but the reaction will not tolerate more than a few ppm of atmospheric moisture or essentially all of the Ac2O autocatalytically decomposes to Me2CO + CO2. Replicating these conditions in an amateur lab isn't that much easier than performing a safe chlorination, since the requirements for atmospheric isolation are similar. To date, no amateur has successfully prepared Ac2O from silver acetate even though this is a known method from reliable papers that isolated the product. By contrast, dozens of people have succeeded with S2Cl2.

IIRC some members experimented extensively with copper acetates to no success, even though these are significantly easier to dry than the zinc compounds.

[Edited on 6-2-2021 by clearly_not_atara]

pip - 6-2-2021 at 08:43

The paper I posted basically confirms the need for an oxygen free environment however it also seems to prove that it’s not simply a mistake in interpreting an acetic acid acetone mixture incorrectly. It also claims that auto decomposition is from too high a temperature.

[Edited on 6-2-2021 by pip]

clearly_not_atara - 6-2-2021 at 08:54

Quote: Originally posted by pip  
The paper I posted basically confirms the need for an oxygen free environment however it also seems to prove that it’s not simply a mistake in interpreting an acetic acid acetone mixture incorrectly. It also claims that auto decomposition is from too high a temperature.

If you're referring to [attached], you should notice that the signal for AcOH is 100x stronger than the signal for Ac2O. This is the highest proportion of Ac2O obtained by a PhD student who dedicated several years of his life to the study of zinc salt decomposition. Even if I accept it all on its face, it's not encouraging.

scaled_1014_for_sm.png - 104kB

[Edited on 6-2-2021 by clearly_not_atara]

pip - 6-2-2021 at 09:43

I agree it’s not promising, my goal was pointing out that the reaction conditions being followed aren’t even the ideal ones. I don’t know if the PHD student ever specifically went for acetic anhydride I didn’t care enough to read the paper past finding out what conditions are more optimal.

Personally I feel that the ketene method is so far superior that the time and effort spent researching this is better used to build an outdoor fume hood with a vent stack that dumps well into the air above you. The fear of ketene is reasonable but that doesn’t mean we can’t plan around it.

clearly_not_atara - 6-2-2021 at 11:07

You expect to get away with a 40' smokestack blowing ketene in your back-yard?

I don't get all of this obsession with "scale". You're not saving time by building a whole building devoted to ketene. Are you planning to become some sort of heroin magnate?

There are plenty of methods that work: S2Cl2, NO2, BzH/TCCA, probably MeCN, and I'm still holding out hope for Cu(OAc)2+SO2.

Fyndium - 6-2-2021 at 15:10

Sometimes the scale of playing safe goes to extremes. Having a gas-tight apparatus with good scrubbing allows for quite ordinary fume hood practices to keep everything safe.

Personally, I have access to a lathe, a mill and a tig welder. These can be used to churn out industrial standard stuff that can easily be proofed to be absolutely gas tight, if it matters. In theory, all is needed is a distillation vessel, hot-torched tube for decomposition of acetone, collection trap for unreacted acetone, and a bubbler with backflow valve to AcOH bath, and a further line to a scrub. Likely it could just be neutralized by feeding the exhaust tube into an incinerator flame, just as oil refineries get rid of the remnants.

The real issue is as you said, building even a very small scale plant for ketene requires some investment for the subject, just to make some acetic anhydride which you will need for...? It's not even so valuable in grey market that it would be worth the trouble to manufacture it for small scale sales.

Usually, for the amateur, a need for small-ish amount arises, and for this metod it is apparently more convenient to do a single batch via chemical synthesis. For some specific stuff, it can well warrant the trouble and the cost of reagents. If then so happens that more would be needed, conditions could be reconsidered. Piloting a synthesis through the most available, not the most economical way is a general practice in many processes, and when the concept is proven, the methods can be perfected by research and trial and error to find the sweet spot for every phase. I though am pretty sure you ain't establishing a chem firm.

[Edited on 6-2-2021 by Fyndium]

pip - 6-2-2021 at 17:41

A bit dramatic huh? 40 foot smoke stack? A roof vent that’s ducted works equally well for a lot more uses than just ketene. If you don’t want a vent in a garage that’s ok, but this method never has been viable, feel free to prove me wrong I hope you do.

The suggestion was simply for those scared of ketene. It is worse than cyanide and all. If you want to play around with milligram amounts zinc is for you. If you think 250ml could only be used for heroin then I guess ok? I want it for chloroacetyl chloride. A nice bifunctional building block.

Spending 6 months to perfect a method that costs a lot of money in trial and error to get enough product to fill a dram container doesn’t sound appealing. Dripping some acetone onto a hot wire and bubbling the gas into some acetic acid is just too easy and reliable. Spend a day doing it (yes, scale) then not have to reproduce the experiment ever again or at least not for years. You can move on to the next project in a day.

I know it’s an amateur forum but I’m simply dumbfounded that scale is being criticized. No one is talking a liter of the stuff.

[Edited on 7-2-2021 by pip]

Fyndium - 7-2-2021 at 00:20

I agree with pip. Some reagents, if needed, can be viable to make a larger batch and store it for years due to setup time.

Volatile non-persistent toxins are much easier to work with than heavy non-volatiles, organometallics etc which cannot be just vented out. First one can disappear on its own in few hours to days at max or easily decontaminated with lye, bleach, ozone etc, latter can require tearing down a building.

clearly_not_atara - 7-2-2021 at 16:32

Fyndium: sorry I don't own a lathe and usually think about stuff that works for people who don't have access to machinery.

Quote: Originally posted by pip  
Spending 6 months to perfect a method that costs a lot of money in trial and error
There's nothing to "perfect". S2Cl2 is well-known and you yourself are planning to work with chlorine so you know it's achievable.

Sure some other low-toxicity methods are more speculative cf. acetonitrile (although this one scales just fine), but we just talk about those because there's more to talk about. 40 feet might be an exaggeration (although it's realistic if you count the horizontal pipe) but six months is a joke.

EDIT: also, you're talking about one hell of a complicated apparatus for a presumably gas-phase reaction between ketene and chlorine...

[Edited on 8-2-2021 by clearly_not_atara]

pip - 8-2-2021 at 07:52

What are you even going on about? Who’s talking about a lathe? The guy that casually mentioned that he’s lucky to have one? It’s not required to build a vent hood.

Please spend all the time and money you want on this, I’ll await your groundbreaking advancements.

Cheer up and stop looking for fights to pick. No one suggests you need a lathe, no one wants gallons of the stuff, no one (hopefully) wants to make heroin. And btw you could make meth or quaaludes just the same with AA along with who know what else it’s so versatile.

Let the OP experiment. If he wants to use the conditions in the paper I linked he could possibly get usable yeilds even if they’re not up to what I personally feel would be a good use of time. If you want to work with other methods feel free, but you don’t need to come in and bring the mood down.

We are hear to learn, experiment, and get advice from peers on better approaches to take. Not criticize, talk down, or just be grumpy.
[Edited on 8-2-2021 by pip]

[Edited on 8-2-2021 by pip]

njl - 8-2-2021 at 07:55

Quote: Originally posted by Fyndium  

Personally, I have access to a lathe, a mill and a tig welder. These can be used to churn out industrial standard stuff that can easily be proofed to be absolutely gas tight, if it matters. In theory, all is needed is a distillation vessel, hot-torched tube for decomposition of acetone, collection trap for unreacted acetone, and a bubbler with backflow valve to AcOH bath, and a further line to a scrub. Likely it could just be neutralized by feeding the exhaust tube into an incinerator flame, just as oil refineries get rid of the remnants.

[Edited on 6-2-2021 by Fyndium]

pip - 8-2-2021 at 08:12

Yeah I edited to address that as you quoted.

clearly_not_atara - 8-2-2021 at 11:52

Quote: Originally posted by pip  
What are you even going on about?

Mostly, I'm trying to point out that you're giving dangerous advice that's also wrong. Ketene isn't the most practical way to make Ac2O, that's either S2Cl2 or S+Br which A: have the most actual proven reports and B: don't require custom-built copper pipes. Before I called you out, you said in at least two posts that the ketene method is a good way to make acetic anhydride, and... it isn't. Unless you have a personal machine shop, of course, that's different.

Nobody should be encouraging anyone to make ketene because it's a bad idea and there are better ones. Seeing as you don't even seem to actually know what the alternatives are, that goes especially for you. If you want to play with ketene, I can't stop you, obviously.
Quote:
If he wants to use the conditions in the paper I linked he could possibly get usable yeilds even if they’re not up to what I personally feel would be a good use of time.

No, there is absolutely no way that any amateur (and for that matter, probably not any professionals) is going to isolate any acetic anhydride by heating zinc acetate, period. You should know that because we both went over the data in said paper.
Quote:
I’ll await your groundbreaking advancements.

This is another example where you don't seem to get the point, I'm talking about methods that have already been proven to work, there's nothing to advance, and furthermore I don't want Ac2O anyway.
Quote:
Not criticize, talk down, or just be grumpy.

Discussion without criticism isn't appropriate for dangerous activities. If you want to discuss without being criticized, you can go post in a forum about anime or something.

pip - 8-2-2021 at 15:56

Waste of time, waste of chemicals, I’ll stick with ketene. But that’s opinion. Acetone is cheap, acetic acid (or just water) is cheap. There’s no multi step process unless you count distilling acetic acid from water or distilling the anhydride.

I already said the zinc method was also a waste of time, but lots of wastes of time turn out to be useful by someone going through trial and error. I won’t discourage him from trying, if I did I do apologize, I will say the same thing youre saying as far as the chances of success are very low. It’s his time to waste and he’d be a little bit of a hero if he can figure it out. I’m not aware of the author of the paper I posted specifically going for AA as his product, it’s possible with optimization he can get a couple percent who knows maybe even 10% or more. Likely, probably not, possible sure.

clearly_not_atara - 8-2-2021 at 16:28

Quote: Originally posted by pip  
Waste of time, waste of chemicals, I’ll stick with ketene. But that’s opinion.

Here's another opinion: it's better to waste a million dollars worth of chemicals than a single human life. A well-built ketene setup will produce a decent amount of AA. A badly built ketene setup will produce a dead body and a story on the six-o-clock news about the dangers of amateur chemistry and (hopefully not) the "Sciencemadness website" that encouraged the decedent to build it.

I still doubt you could build a ketene setup faster than gassing some sulfur with chlorine and react the product with acetic acid. I believe Fyndium could build a ketene setup because he demonstrated in the first sentence he understood what it requires.

Look, ketene is achievable, but it absolutely should not be your first high-temperature gas-phase reaction. Likewise, you should not attempt to pilot the first boat you build across the Atlantic Ocean. If your plan is to go from "never performed a gas-flow reaction above 100 C" to "successfully made ketene" and you think you're going to save time and money relative to chlorinating sulfur, you're out of your mind.

https://www.ncbi.nlm.nih.gov/books/NBK224928/

"Like phosgene, the pulmonary effects of inhalation exposure to ketene may be manifested in the absence of direct irritation by ketene or its breakdown product, acetic acid."

[Edited on 9-2-2021 by clearly_not_atara]

pip - 9-2-2021 at 09:09

There must be something wrong with you. You just look for arguments, get help man.

Bubbling ketene twice and venting the tiny amount that makes it past both containers with a high powered fan will be more than adequate.

I have a feeling you’ve never actually done it.

[Edited on 9-2-2021 by pip]

njl - 9-2-2021 at 09:12

It would have cost you nothing to not say that.

pip - 9-2-2021 at 09:21

Enough is enough, this guy needs to take his mental health issues out in someone else.

clearly_not_atara - 9-2-2021 at 09:34

Quote: Originally posted by pip  
Enough is enough, this guy needs to take his mental health issues out in someone else.

If you actually knew what you were doing, I wouldn't be so critical. It's pretty clear that you can neither respond to my arguments nor use ketene safely. Having revealed that to everyone, I've accomplished something.

pip - 9-2-2021 at 09:43

Only thing you’ve accomplished is proving that you argue just to argue, you haven’t contributed anything of substance to the conversation. Repeating that zinc acetate isn’t a good method isn’t anything new. Posting synthesis methods already known isn’t contributing. The only thing you’ve successfully done is derail the conversation. Even when I tried to put it back on track by agreeing that I wouldn’t do the zinc method because I prefer ketene, but I do support the OP experimenting with zinc under different experimental conditions you choose to pick a new argument about the method I personally prefer as if that somehow affects you personally.

Can we get back to the topic now? Is that ok with you?

clearly_not_atara - 9-2-2021 at 10:05

Quote: Originally posted by pip  
you haven’t contributed anything of substance to the conversation.

You realize it was me who read through the 200-page PhD thesis you posted and highlighted the yields for everyone, correct?

pip - 9-2-2021 at 14:18

Are you done yet?

Let the guy experiment, no one needs your blessing

[Edited on 9-2-2021 by pip]

ChemichaelRXN - 10-2-2021 at 02:13

I dont need acetic anhydride, but I was thinking, do you think reacting 2 moles of acetic acid with the catalyst H-beta-zeolite would form the acetic anhydride? I have seen a number of reactions where diols are joined, but maybe steric hindrance from the ketone group of carboxylic acid would prevent it. Not sure...

There are a number of things you can do with h-beta-zeolite.
Esters. https://www.mdpi.com/2073-4344/9/9/758/htm
Amides. http://nopr.niscair.res.in/bitstream/123456789/40904/1/IJCA%...
Cyclization joining diols. https://pubs.rsc.org/en/content/articlelanding/2018/gc/c7gc0...

Very versatile. If anyone want some for free i have about 25 grams x 3 of h-beta-zeolite I will give away, just PM me!

[Edited on 10-2-2021 by ChemichaelRXN]

36C0EC49-8303-4525-9D25-748EC5A1A8A1.png - 79kB98C90D0A-A229-4264-A72F-3D463E424EF7.png - 463kB

symboom - 10-2-2021 at 06:41

acetic anhydride is prepared by the reaction of ketene (ethenone) with acetic acid at 45–55 °C and low pressure (0.05–0.2 bar).

I hope the paper that states that zinc acetate is not referring to acetone first produced (as an intermediate) then cracked into acetic anhydride
Simular to calcium acetate gives off acetone when heated too.
It maybe possible that it is generated directly. Has anyone attempted to use other transition metal acetates.

If acetic acid can just be dessicated under vacuum using calcium chloride, magnesium sulfate, sulfuric acid or phosphorous pentoxide.

Here is from prep chem
acetic anhydride was prepared by placing 20 grams of dry acetic acid in a flask, fitted to a condenser and then dropping 20 grams of oxalyl chloride in the acetic acid. The water was removed from the acid by freezing it in a freezing mixture until there was just a little liquid left in the center.

Wow apperently Acetic anhydride can be used as a dehydrating agent for the formation of anhydrides.

Acetic anhydride can also by obtained from an anhydrous sodium acetate and phosphorus oxychloride. From practical point of view it is not necessary for the preparation of acetic anhydride isolate the acetyl chloride; it is better to allow acetyl chloride to act directly on an excess of the anhydrous sodium acetate, so that from the phosphorus oxychloride and anhydrous sodium acetate the acetic anhydride is directly obtained

Here is silver acetate
A solution of silver acetate in pyridine absorbs hydrogen, producing metallic silver and anhydrous acetic acid

2 CH3CO2Ag + H2 → 2 Ag + 2 CH3CO2H


[Edited on 10-2-2021 by symboom]

pip - 10-2-2021 at 06:55

Phosphorus pentoxide does form acetic anhydride in acetic acid. But it’s not the easiest chemical to get a hold of. Some of us can, some of us can’t. That’s why ketene is still the preferred method for a lot of people. It’s downsides are outweighed by its simplicity. There’s a lot of YouTube ketene videos that cover it well. Including the fact that while ketene and water will make acetic anhydride, you have to stop at 70% acetic acid, distill the acid to remove the water, then continue. For some reason polymerization becomes a problem past 70% acetic acid without first removing the water.

clearly_not_atara - 10-2-2021 at 07:36

Quote: Originally posted by symboom  
acetic anhydride is prepared by the reaction of ketene (ethenone) with acetic acid at 45–55 °C and low pressure (0.05–0.2 bar).

Come on, you know better than this.
Quote: Originally posted by ChemichaelRXN  
I dont need acetic anhydride, but I was thinking, do you think reacting 2 moles of acetic acid with the catalyst H-beta-zeolite would form the acetic anhydride? I have seen a number of reactions where diols are joined, but maybe steric hindrance from the ketone group of carboxylic acid would prevent it. Not sure...

There's a lovely thread about acetic anhydride in general. It's stickied.
Quote: Originally posted by pip  
That’s why ketene is still the preferred method for a lot of people. It’s downsides are outweighed by its simplicity.

No, ketene is a dangerous, stupid idea that nobody should be encouraged to pursue. I thought I explained this to you. There's one video from Doug's Lab and even his fans pointed out he was being reckless.

Chlorine, bromine, hydrogen chloride and other dangerous gases used for this become irritating long before they become toxic. Ketene can become toxic before it becomes irritating. There's a reason nobody encourages it here.

Also, plenty of people failed at using phosphorus pentoxide in the Ac2O sticky. It's easy to end up with "charred black crap". You would know this if you bothered to do your homework.

[Edited on 10-2-2021 by clearly_not_atara]

pip - 10-2-2021 at 12:56

What part of no one cares what you have to say are you not getting? Stop with the personal mission of discouraging others from doing something because you can’t do it safely. How many more posts are you going to make regurgitating the same crap? You’re against it, we get it, now move on.

I guess this paper is fake then...

https://www.ijraset.com/fileserve.php?FID=24897

[Edited on 10-2-2021 by pip]

Texium - 10-2-2021 at 14:17

You're the one in the wrong here, pip. Atara is spot on about the risks of the ketene procedure that you are being so blasé about. It's not "preferred for a lot of people." You can probably count the number of amateurs who actually use it on one hand. Who knows, maybe you're one of them.

You need a really good fume hood. Not just a box with a fan blowing out of it. You need to be certain that all of the air inside of it is circulated. You need a purpose-built apparatus. Not some cobbled together glassware that could pop open at any moment. And finally, you need experience working with other gases that are less dangerous so that you realize just how easy it is for traces of gas to escape even the best of hoods. Maybe you have all that, pip, maybe you don't. I don't care whether you do it or not. The problem is how you casually suggest it as if it's something that everyone should be doing.

As for this thread, zinc acetate is clearly a dead end. Other methods for acetic anhydride can be discussed in the sticky.