EvlRenne
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Hazardous concerns
Hello everyone!
Guys, in my upcoming synthesis, there is a one step, which I worry about quite a lot.
I'm about to do reaction between dimethyl benzyl carbinol + acetonitrile and conc. H2SO4.
I was searching the web and as usual found 2 opposite answers...
Question is, will be produce gaseous HCN during the reaction above?
I was reading few topics, which are saying that during nucleophilic substitution there is no HCN production, and at the same time some people are
saying that H2SO4 + C2H3N will produce HCN.
I need your help for obvious reason, I don't want to die *_*
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Swinfi2
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My recommendation is to (safely) test if you have the right genetics to smell HCN, it smells like almonds or absolutely nothing. I'd only do this if i
know theirs no risk or I can smell it and be able to know if it's gone wrong and get away from it. As for the chemistry, I'm not the right person to
ask with this one.
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Atrum
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Hazard to self is pretty damned accurate, Swinifi2
"Experience is my one true mistress and I will cite her in all cases. Only through experimentation can we all truly know anything." ~Leonardo da Vinci
My inventory
Recently acquired elements: Iodine , Cobalt, Tungsten, Silicon |
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DavidJR
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I can't find any references stating that acetonitrile + sulphuric acid can produce HCN. It doesn't seem very likely to me.
Pyrolysis and incomplete combustion of acetonitrile can, however, produce HCN.
I have also heard that technical grade acetonitrile may contain free HCN as an impurity.
[Edited on 31-10-2018 by DavidJR]
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Swinfi2
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I didn't exactly tell him to gas himself with HCN to see if it was HCN *facepalm*, there are many ways to do the same thing. Ex: https://youtu.be/d1rUw21MIII
Not knowing if you are sensitive (or insensitive in a potentially non-ideal situation) to a potential hazard seems more reckless if you ask me.
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AvBaeyer
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The reaction described by OP is the "Ritter reaction." There is no chance of HCN evolution from this reaction. I do not know of any normal reaction
conditions involving H2SO4 and acetonitrile that will produce HCN.
AvB
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zed
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Well, seems to me, the methyl radical is pretty rapacious.... Meaning not very stable... Meaning unlikely to allow significant hydrolysis of
acetonitrile to methanol and HCN. But, that isn't the final word, and acetonitrile itself is quite toxic if you are exposed to a significant amount
of it.
Your body can convert acetonitrile to HCN, internally. When acetonitrile use, migrated from closed industrial systems, into common lab use, there
were a fair number of surprise deaths reported.
I would expect more HCN release during hydrolysis of Phenylacetonitrile, whereas the benzyl radical, being more stable, might be more easily shuck off
HCN.
As always, proceed with caution. https://www.youtube.com/watch?v=Tc2UamEkRjk
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DavidJR
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Quote: Originally posted by zed  | | But, that isn't the final word, and acetonitrile itself is quite toxic if you are exposed to a significant amount of it. |
It is moderately toxic, but it's actually quite significantly less toxic than other small nitriles.
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AvBaeyer
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Zed,
I have never in many years heard of any deaths related to lab use of acetonitrile. Can you support your statement with references to some reports? We
used to run benchtop HPLC using gallons of acetonitrile every week. No one died or became ill. All waste streams were dumped down the drain. Can you
also document any experimental eveidence for HCN formation from phenylacetonitrile hydrolysis? Its hydrolysis does not involve any free radical
formation that I have ever heard of.
AvB
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DavidJR
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| Quote: Originally posted by AvBaeyer | Zed,
I have never in many years heard of any deaths related to lab use of acetonitrile. Can you support your statement with references to some reports? We
used to run benchtop HPLC using gallons of acetonitrile every week. No one died or became ill. All waste streams were dumped down the drain. Can you
also document any experimental eveidence for HCN formation from phenylacetonitrile hydrolysis? Its hydrolysis does not involve any free radical
formation that I have ever heard of.
AvB
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I was thinking this too. I found a few reports of deaths/poisonings with MeCN but none were lab workers. There have been a few children who have died
as a result of ingesting acetonitrile based nail polish remover, including one case in the UK where this was misidentified as acetone and no cyanide
antidote was given.
Also, I find it interesting that when I ordered solvents for my HPLC recently the delivery box had big warning stickers re the toxicity of methanol,
but not about acetonitrile.
P.S. routinely disposing of large quantities of either MeCN or MeOH down the drain seems environmentally irresponsible, if not outright illegal
(depending on location).
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zed
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There was a minor epidemic of Acetonitrile deaths, about 40 years ago.
Enough of them, that alerts were circulated.
Apparently, Acetonitrile proved less dangerous than initially feared.
That is not to say, it is non-toxic. It is toxic, if you get enough exposure, or if you happen to inhabit the wrong end of the bell curve.
So, as Clint Eastwood would say: "Are you feeling lucky?"
https://pmj.bmj.com/content/postgradmedj/73/859/299.full.pdf
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AvBaeyer
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Zed,
Thanks for the reference. The paper refers to an attempted suicide by acetonitrile ingestion and may not be entirely relevant to normal lab exposures.
Nonetheless, I was unaware of P450 oxidative metabolism of acetonitrile in such a manner that cyanide was produced. I learn something new every day!
DavidJR,
I should have put my acetonitrile disposal comment in context. That happened back in the late 1970's when I was employed by a major pharma in New
Jersey. Water miscible solvents just went down the drain, sometimes in fairly large quantities. We collected non-water miscible solvents and highly
contaminated solvents (eg, acetone, ethanol, etc) in waste containers for off site disposal. No effort was required to separate chlorinated,
hydrocarbon or other solvents into separate streams - it cost too much. That's all changed now.
At that time, I also worked in a 6-person lab with two shared 5-foot hoods. Needless to say, almost all chemistry but that which was malodorous was
carried out on the bench. Roto-vaps, vacuum pumps, and solvent stills were also set up outside hoods. All chromatography, preparative and analytical,
was run on the bench top. I ran butyl lithium reactions (and worse) at my bench. I should point out that we ran most reactions on relatively small
scale - 100 ml flasks and smaller, mostly 14/20 glassware. There were a couple of old-timers in the lab that on Friday before going home would clean
the droppings on there bench tops with benzene or chloroform or whatever else might be handy and evaporate quickly. Of the 6 of us that worked in that
lab, 4 of us are still going strong (70+ years old) and the other two died well into their 80's. The point of all this is that toxicity of most
chemicals in a laboratory setting is in my opinion quite overblown. Hell, we even used Magic Methyl before it was banned and survived. Enough about
the old days. Things have changed with the advent of easy admission to law schools. Got to keep the lawyers busy peering under every rock looking for
monetizable risks.
AvB
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Panache
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A recent NIH longitudinal study into the cause of cancers in humans, setup to understand whether the ad hoc explanation that50% of cancers were
environment based (ie chemicals etc) and the remainder just genetic showed, that actually only 7% were environment based, meaning of course our
fascination with labelling anything and everything a carcinogen is just plain wrong.
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DavidJR
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| Quote: Originally posted by AvBaeyer |
I should have put my acetonitrile disposal comment in context. That happened back in the late 1970's when I was employed by a major pharma in New
Jersey. Water miscible solvents just went down the drain, sometimes in fairly large quantities. We collected non-water miscible solvents and highly
contaminated solvents (eg, acetone, ethanol, etc) in waste containers for off site disposal. No effort was required to separate chlorinated,
hydrocarbon or other solvents into separate streams - it cost too much. That's all changed now.
At that time, I also worked in a 6-person lab with two shared 5-foot hoods. Needless to say, almost all chemistry but that which was malodorous was
carried out on the bench. Roto-vaps, vacuum pumps, and solvent stills were also set up outside hoods. All chromatography, preparative and analytical,
was run on the bench top. I ran butyl lithium reactions (and worse) at my bench. I should point out that we ran most reactions on relatively small
scale - 100 ml flasks and smaller, mostly 14/20 glassware. There were a couple of old-timers in the lab that on Friday before going home would clean
the droppings on there bench tops with benzene or chloroform or whatever else might be handy and evaporate quickly. Of the 6 of us that worked in that
lab, 4 of us are still going strong (70+ years old) and the other two died well into their 80's. The point of all this is that toxicity of most
chemicals in a laboratory setting is in my opinion quite overblown. Hell, we even used Magic Methyl before it was banned and survived. Enough about
the old days. Things have changed with the advent of easy admission to law schools. Got to keep the lawyers busy peering under every rock looking for
monetizable risks.
|
Interesting - times have certainly changed.
Regarding waste solvents: if you practice strict segregation then recovery of the solvents becomes economical, either yourself or by selling the waste
to a solvent recovery company. Seems such a waste to dispose of countless litres of mildly-contaminated MeOH/H2O or MeCN/H2O
waste from an HPLC. The more you mix waste of different types the more difficult/expensive it becomes to separate and recover the valuable resources
it may contain.
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Dr.Bob
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Ritter reaction should be fine, no real risk of HCN generation, but the amount of sulfuric used does make the reaction a joy to work up, so be careful
when quenching it. Good luck with the reaction, it works pretty well, but is not real clean due to side reactions.
I can second AvBaeyers that things have changed dramatically since I started. I ran benzene flash columns, worked in labs without much ventilation
(I taught organic labs (with 2 others) in a 50 person lab with 4 small fume hoods), most rotovaps were on the bench and hooked to aspirators for
vacuum, taking much solvent down the drain, and much more. But again, many people I worked with are still doing well in their 80s and 90's,
including my friend Ed, who worked with fluorine, HF, and even the dreaded ClF3 a few times, and is going strong in his 90's, so even substantial
chemical exposure did not seem to harm them, compared to others.
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DavidJR
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| Quote: Originally posted by AvBaeyer |
Of the 6 of us that worked in that lab, 4 of us are still going strong (70+ years old) and the other two died well into their 80's. The point of all
this is that toxicity of most chemicals in a laboratory setting is in my opinion quite overblown. Hell, we even used Magic Methyl before it was banned
and survived.
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| Quote: Originally posted by Panache | A recent NIH longitudinal study into the cause of cancers in humans, setup to understand whether the ad hoc explanation that 50% of cancers were
environment based (ie chemicals etc) and the remainder just genetic showed, that actually only 7% were environment based, meaning of course our
fascination with labelling anything and everything a carcinogen is just plain wrong.
|
| Quote: Originally posted by Dr.Bob |
But again, many people I worked with are still doing well in their 80s and 90's, including my friend Ed, who worked with fluorine, HF, and even the
dreaded ClF3 a few times, and is going strong in his 90's, so even substantial chemical exposure did not seem to harm them, compared to others.
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Recently I was given a [patronising] telling off by my step aunt (who has a undergrad chemistry degree but works in software) for handling a vial of
copper phthalocyanine (a remarkably inert blue pigment) without gloves on. Later, I mentioned this to my 76 year old grandfather, whose career in the
dyestuffs industry doesn't seem to have done him much harm - despite being known to come home covered in green/blue. Specifically, he chlorobrominated
copper phthalocyanine (marketed as Monastral Fast Blue) to produce Monastral Fast Green, at ICI Grangemouth, where the phthalocyanines were
discovered.
I certainly agree that there's a lot of risk exaggeration that goes on re the health effects of all sorts of chemicals. It does seem that nowadays
everything is considered a potential carcinogen to be avoided. But then again, when it comes to chronic toxicity, perhaps caution is not a bad thing.
However: it is clear that us humans have become a plague on earth. We've done an excellent job of royally fucking up this planet which no other
species can come close to. So frankly we all have a responsibility to work in sustainable and ecologically-friendly ways - such as by recycling waste
solvents into useful products, rather than pouring them down the drain.
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AvBaeyer
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DavidJR,
I do not want to drag this out too far but I need to comment on the idea of recycling solvents in an industrial research lab environment. I gather
from your comments, hopefully correctly, that you have no industry experience. First, many solvents are mixed as a result of running reactions and
workup. These solvents may not be easily separable or chemically compatible for recycling. Second, having collection vessels spread throughout a lab
space for each solvent type or class is just not practical. Most importantly, recycling solvents is not cost effective, at least it was not several
years ago, especially if you want to recover highly pure lab useful solvents. Take, for example, HPLC effluent based on acetonitrile. This contains
not only acetonitrile but also water, trifluoroacetic acid and/or various buffers some of which may be volatile. Recovering HPLC grade acetonitrile
from this mix is not trivial nor cheap. Similar situations exist with other solvent mixtures, for example, ethyl acetate-hexane mixtures. When I was
heading up a sizable discovery chemistry department I was berated by my CEO (a sarcastic but loveable Brit accountant) regarding our solvent purchase
and disposal expenses. I was tasked with looking into recycling our waste stream for either internal use or getting some value from it. After spending
more time than it was worth it turned out that we could not find anyone to deal with our "low" output of waste for recycling. We were told the
economics did not make sense. Moreover, our waste stream had no residual value for other uses after accounting for costs of hauling it away. It just
came down to the basic economics of running a research operation (time is money, do not waste it.) Perhaps things are different now but I cannot say.
The foregoing is dealing with waste solvents in a research lab situation. My experience when running a process development lab is quite different.
Processes were developed to minimize solvent use and if possible reuse recovered solvents in a process. It's an entirely different world with regard
to economics (and environmental concerns) when compared to a basic research lab environment. Solvent use can be enormous as are disposal costs if you
cannot reuse.
AvB
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EvlRenne
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Thanks to all of you guys, regarding the answers about my topic, I was searching information myself and found, that it could be dangerous when your
exposed to it for a long time within huge concentration in the air or when you absorb it via skin / eyes it metabolize into CN and you start to suffer
CN poisoning symptoms.
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DavidJR
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| Quote: Originally posted by AvBaeyer |
I do not want to drag this out too far but I need to comment on the idea of recycling solvents in an industrial research lab environment. I gather
from your comments, hopefully correctly, that you have no industry experience. First, many solvents are mixed as a result of running reactions and
workup. These solvents may not be easily separable or chemically compatible for recycling. Second, having collection vessels spread throughout a lab
space for each solvent type or class is just not practical.
|
You're correct that I have no industry experience. I get that sometimes solvents will be mixed in reactions etc, and if using smallish quantities of
large numbers of different solvents it may be impractical to recycle in any way other than combining the lot and sending off for disposal, e.g.
incineration for energy recovery.
| Quote: Originally posted by AvBaeyer |
Most importantly, recycling solvents is not cost effective, at least it was not several years ago, especially if you want to recover highly pure lab
useful solvents. Take, for example, HPLC effluent based on acetonitrile. This contains not only acetonitrile but also water, trifluoroacetic acid
and/or various buffers some of which may be volatile. Recovering HPLC grade acetonitrile from this mix is not trivial nor cheap.
|
I'm sure you are aware that producing HPLC-grade solvents is non-trivial in the first place, even starting from virgin reagent grade material. I don't
think it's necessarily particularly practical to recycle HPLC eluent waste into HPLC-grade solvents.
But that doesn't mean the waste is worthless. It's relatively easy to segregate solvent systems by switching out the waste container as appropriate.
The contamination from buffers, additives, and the samples themselves, are going to be <1%. HPLC waste is probably one of the easiest sources of
waste solvent to recycle into a useful product, because you started with very pure solvents and added only very small concentrations of contaminants.
Fractional distillation would be necessary to remove most of the water, of course, which would probably go a fair way to removing buffer salts too. At
that point you then have mostly pure methanol or acetonitrile (azeotrope w/ water unfortunately) which could well be used for many non-critical
applications.
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unionised
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Concentrated sulphuric acid will catalyse the condensation of acetonitrile to cyclic trimers
This reaction can become violent.
It's not HCN I'd worry about.
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