chempyre235
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Cost-Effective Preparation of Alkyl Nitrile Solvents
I recently came across a Wikipedia article that showed a possible synthesis of propionitrile from distillation of ethyl sulfate with potassium cyanide. From one of my
organic chemistry textbooks (which I'll have to reference later), sulfate esters can form from addition of an alcohol to concentrated sulfuric acid at
relatively low temps (even 0°C for ethanol). In theory, I'd imagine this could also be used to make several useful nitriles from other alcohols as
well, such as methanol (to make acetonitrile), isopropanol (to make isobutyronitrile), and t-butanol (to make pivalonitrile). If this works,
it could make these reagents inexpensive, without having to use strong dehydration agents like P4O10.
EtHSO4 + KCN ---> EtCN + KHSO4
In short:
MeOH ---> MeCN (Acetonitrile)
EtOH ---> EtCN (Propionitrile)
i-PrOH ---> Me2CHCN (Isobutyronitrile)
t-BuOH ---> t-BuCN (Pivalonitrile)
ROH ---> RCN
I'd like to hear from everyone -- is this a good idea, or would this not be a worthwhile pursuit?
P.S. One issue I see with some of the secondary/tertiary alcohols is that they'd sooner dehydrate than form sulfate esters. Is there any way that this
can be prevented? A buffer or diluent maybe?
"However beautiful the strategy, you should occasionally look at the results." -Winston Churchill
"I weep at the sight of flaming acetic anhydride." -@Madscientist
"...the elements shall melt with fervent heat..." -2 Peter 3:10
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clearly_not_atara
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I don't think that any reaction involving KCN can be "cost effective" for the amateur when the equipment required to simply store and handle the
substance is already nontrivial.
Then you combine it with an acid? Surely we should be talking about using NaSO4Me here, right?
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chempyre235
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I found another reference, this time indicating that the barium salt is used.
| Quote: |
Heating barium ethyl sulfate and potassium cyanide with subsequent distillation.
Lewis, R.J., Sr (Ed.). Hawley's Condensed Chemical Dictionary. 13th ed. New York, NY: John Wiley & Sons, Inc. 1997., p. 465
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https://pubchem.ncbi.nlm.nih.gov/compound/Propionitrile#sect...
Perhaps the Wikipedia author meant diethyl sulfate? They didn't cite the source for that remark, so I don't know for sure.
[Edited on 9/15/2025 by chempyre235]
"However beautiful the strategy, you should occasionally look at the results." -Winston Churchill
"I weep at the sight of flaming acetic anhydride." -@Madscientist
"...the elements shall melt with fervent heat..." -2 Peter 3:10
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davidfetter
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There appear to be some promising avenues via electrochemistry. I don't know whether they make it easy to produce solvent amounts of those nitriles,
but I thought people might be interested.
ETA: the actual paper. Oops.
Attachment: electrosynthesis_of_nitriles_from_primary_alcohols_and_ammonia_on_ni_catalyst_d5gc00572h1.pdf (3.6MB)
This file has been downloaded 90 times
Attachment: electrosynthesis_of_nitriles_from_primary_alcohols_and_ammonia_on_ni_catalyst_d5gc00572h.pdf (3MB)
This file has been downloaded 71 times
[Edited on 2025/9/16 by davidfetter]
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bnull
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First of all, be careful with Wikipedia. It is based on voluntary work and, as it happens with activities that involve voluntary work, quality varies;
not every editor has a PhD in the field they're editing (take it from yours truly, who hasn't even completed his BSc). It is a wonderful effort but it
has issues (bad sentences, lack of sources, partiality, as can be seen to some extent in the article on Freestyle typescript). I suppose you remember
"The Adventure of the Missing Copper Salt" (https://sciencemadness.org/whisper/viewthread.php?tid=160825...).
By the way, the source for the "possible synthesis of propionitrile from distillation of ethyl sulfate with potassium cyanide" comes from the Merck
Index (1996), p. 1345. It is also mentioned in the PubChem link you shared, under 9.2 Methods of Manufacturing.
Quote: Originally posted by chempyre235  | | One issue I see with some of the secondary/tertiary alcohols is that they'd sooner dehydrate than form sulfate esters. Is there any way that this can
be prevented? A buffer or diluent maybe? |
Have you considered metathesis? Polyvinyl acetate reacts with alcohols in the presence of base to form polyvinyl alcohol and alkyl acetates. Perhaps a
similar process, using potassium polyvinyl sulfate (KPVS) with the secondary/tertiary alcohol and a catalytic amount of KOH, can produce potassium
alkyl sulfates.
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Fery
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This is proven way, but has more steps.
CxHx+1OH + HBr -> CxHx+1Br
CxHx+1Br + KCN -> CxHx+1CN
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chempyre235
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Thanks all for your responses! It looks like this synthesis will need quite a bit more thought and research. For now, I'll have to set this problem
aside, but maybe I'll come back to it. 
"However beautiful the strategy, you should occasionally look at the results." -Winston Churchill
"I weep at the sight of flaming acetic anhydride." -@Madscientist
"...the elements shall melt with fervent heat..." -2 Peter 3:10
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Radiums Lab
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The halide process is more better in my opinion. Cyanide can be synth. using urea.
Water is dangerous if you don't know how to handle it, elemental fluorine (F₂) on the other hand is pretty tame if you know what you are doing.
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Lionel Spanner
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I know you can make alkyl hydroperoxides by displacing the relevant alkyl ester of sulphuric acid with hydrogen peroxide at room temperature. But I
have a strong feeling that attempting the same process with cyanide salts would be a lot less simple, as cyanide ions are a lot more basic than
hydrogen peroxide, and the excess of conc. sulphuric acid present in the mixture would result in the formation of hydrogen cyanide, possibly some
oxidation products too.
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clearly_not_atara
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FWIW, this was never necessary:
http://www.sciencemadness.org/talk/viewthread.php?tid=11137&...
I think the bigger problem with making acetonitrile, at all, or any solvent, is that usually you can't make enough of a solvent to fill (usefully)
your largest reaction vessel. You need an even larger vessel, which will generally offer a small fraction of its volume as the product (desired
solvent) after one run of the reaction.
In practice, it is rare for people to make solvents in order to use them, even solvents with a simple, widely-known prep like diethyl ether. It adds
another step (or several more steps) to the procedure you actually want to do, and it requires you to work at a larger scale than you would have
otherwise -- if you had bought the solvent. Even before we talk about dehydrating acetamide, you have to make acetamide, which has an expected 50%
yield by heating ammonium acetate, oh and you probably have to make ammonium acetate too. Or if you start with methylsulfate and potassium cyanide,
then you have to make methylsulfate and you'd better be pretty slick on the phone convincing the chemical company rep to ship you some KCN.
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clearly_not_atara
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I found an article that discusses the simple pyrolysis of amides to nitriles in detail. It appears that mechanical catalysis, as the authors
describe "finely divided solids", are important for ensuring a good yield of nitrile. This has to do with the surprisingly complex mechanism of
dehydration:
2x amide >> ammonia + iso-imide, RC(NH)OC(O)R
iso-imide >> nitrile + acid
acid + ammonia >> amide + water
Only when the reaction occurs in a complete "cycle" do you obtain >50% yields of nitrile. In particular, phenylacetonitrile is obtained efficiently
from phenylacetamide, even though benzonitrile is difficult to obtain from benzamide.
Attachment: davidson1956.pdf (443kB)
This file has been downloaded 71 times
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