HCN, NaOH and BzCN

[blondie]

swim is looking at the possibility of preparing an aqueous solution of KCN by bubbling HCN into NaOH (from H2SO4 + K ferrocyanide)

https://www.thevespiary.org/rhodium/Rhodium/chemistry/nacn.txt

His question is how to obtain a neutral aqueous solution of NaCN? (risk of liberating free HCN)

alternatively if a still basic solution of NaCN (excess NaOH remaining) was used in the benzyl cyanide synth

https://www.thevespiary.org/rhodium/Rhodium/chemistry/benzylcyanide.html

, would this be a problem? if some of the benzyl chloride reacted (immediately?) with the NaOH this might only affect yields.

also see

Post 76846 (missing)

(Bwiti: "Sodium Cyanide", Chemistry Discourse) Bwiti asked a similar question.

[Osmium]

Before you try anything like that you have to learn the basics.
For example that NaCN dissolved in water isn't neutral, but always basic. Evaporating a neutral solution of NaCN will liberate HCN. Evaporating a basic solution won't.

[Elementary]

The way I dreamed of doing it was to excess on the HCN in the NaOH pot and then remove the excess of HCN but heating the solution in a fume cupboard.

The whole procedure should be done in a fume cupboard idealy or outside while wearing protective clothing and a gasmask.

Please please be carefull, you done get any second chances with cyanide !
One day I'll understand everything !

[PolytheneSam]

I think CO₂ in the air can displace the CN-, ie.

CO₂ + H₂O --> H₂CO₃
NaCN + H₂CO₃ --> NaCO₃ +HCN

BTW, one time when I made some sodium aluminate from Red Devil Lye and aluminum foil, after I filtered it and let it stand for a while (2 days?) a precipitate formed which I didn't expect.  I figured it was alumina which I was trying to make in the first place and it saved me the trouble of adding acid to precipitate the alumina.  After that I found something in a chemistry book in the library where it said (and showed equations) that CO₂ in the air can displace the alumina.  Also, after that I heated the fine hydrated alumina ( Al(OH)₃ ) powder I got in an evaporating dish on a hot plate (to get Al₂O₃ ) and noticed little bubbles coming up through the dry powder.  I left it out and it hardened and I broke it up into pieces.
http://www.geocities.com/dritte123/PSPF.html

[blondie]

Elementary,

you suggest excessing the HCN in the NaOH. Then heating the solution (to boiling) to rid all the dissolved HCN - obviously piping this into a second pot of NaOH. whats the best way to monitor the excess point - no more uptake from the HCN generator or by pH (what level?). I feel that the preparation on Rhodiums page is not complete without a few more details - particularly if excessing then the requirement of a second vessel of NaOH.

this is not for p2p otherwise id do a grignard or knoevenagel condensation. i dont see many other feasable routes to BzCN. both BzCN and alkali metal cyanide salts are impossible to buy here.

thanks to the bees for their help.

[PPyroReached600]

Didn't jim post the reaction of

CHCl3 + 4NaOH + NH3 ==H2O==> NaCN + 3NaCl + 4H2O

I believed he called it the (something) isonitrile synthesis. When chloroform is used with sodium hydroxide, the HCN produced reacts with the alkalai, forming the salt.

Hey, Elementary, wouldn't that be a candidate for your acetonitrile synthesis?

1,1,1-trichloroethane + ammonia + 3NaOH --> MeCN + 3NaCl + 3H2O

                                                    PrimoPyro
Guess who exceeded his alotted Hive bandwidth today?

[Elementary]

No the heat would drive off the HCN in the solution, leaving you with just NaCN and Water. I know the boiling point of HNC is 25.86°c, not sure if it forms a constant boiling liquid with water ?

Polythenesam, the CO2 possibly entering the solution while the HCN is being driven out by warming will be very small if any.


One day I'll understand everything !

[halfapint]

1,1,1-trichloroethane + ammonia + 3NaOH --> MeCN + 3NaCl + 3H2O

Gotta bee somethin wrong. Can't tell me it's that easy.

Pyro burnin up the data channels, yow.
turning science fact into <<science fiction>>

[PPyroReached600]

Dear god! I completely take back the 1,1,1-trichloroethane reaction! That is one fucking expensive material! Totally not worth the money if used for this reaction.

$138/500mL or $377/4L

Holy shit!

                                                PrimoPyro
Guess who exceeded his alotted Hive bandwidth today?

[blondie]

PrimoPyro made a couple of posts last night before i went home - ive just got out of bed and hes still online . ill see if i can find a write up of the chloroform, lye and ammonia prep.

Elementary, i understand that you drive off disolved HCN gas leaving the desired NaCN and water. The second pot is just to avoid the unwanted HCN venting outside the system. i hadnt considered the possibility of an azeotrope though.

[jim]

The Hoffman isonitrile synthesis...  Only works with primary amines, like NH3

[Aurelius]

Jim, have you tried running the Hoffman isonitrile synthesis?  (the one above in particular)  if so, do you have exact numbers for it?  do you think it could be run in a "kitchen chemistry" style, or will it have to be more exact?  (kitchen chemistry does not denote lack of safety precautions, just want to avoid the task of measuring everything exactly)

[halfapint]

Hm, the Hofmann isonitrile synthesis corresponding to aceto(iso)nitrile would bee methylamine + chloroform + NaOH; for benzyl (iso)cyanide, it should come from benzylamine, chloroform, and NaOH.
~ ~ ~ ~ ~ C U N D C ~ ~ ~ ~ ~ ~
~ ~ four twenty oh oh three ~ ~

[PrimoPyro]

What the hell is an isocyanide? HNC=? HNC=H2? HNCH-CH3?

benzonitrile would be PhCN. What would be benzoisonitrile? PhNC=? The bonds don't add up. Ph-N=C=?
Vivent Longtemps la Ruche!

[blondie]

Uemura dreamed about the isonitrile synth with ammonia some time ago and did a write up

Post 57287 (missing)

(uemura: "Dreams of a KCN synthesis", Methods Discourse). seems to be a lot of unknown variables still - and not just in the workup. without a good prep or ref to follow blondie thinks this is outside her comfort zone .

[uemura]

Uemura dreamed about the isonitrile synth with ammonia some time ago

Yes he did, but no comments nor good nor bad.

Just jim did once refer to this isonitril synthesis....

Carpe Diem

[Rhodium]

Benzoisonitrile is indeed Ph-NC with a tetravalent nitrogen and a trivalent carbon (and all the resonance forms you can think of).

[PrimoPyro]

That can't be stable!  

So do all isonitriles rearrange to nitriles with heating? If not, they should either decompose, or polymerize somehow. This is not stable without special conditions.

                                                     PrimoPyro

P.S. Rhodium: I had looked at a lot of chemfinder data and reached the same conclusion, but didnt want to post about it, as everyone seems to understand it while I dont.  
Vivent Longtemps la Ruche!

[Rhodium]

NO (nitric oxide) and CO (carbon monoxide) is also of this type of bond, so it can be relatively stable.

However, isonitriles are very reactive, forming carbamates with alcohols, and is hydrolyzed by anything acid.
And yes, isonitriles are prone to polymerize, forming urethanes with polyhydric alcohols for example.

[PrimoPyro]

Thanks Rhodium. Good to know, and very interesting. I dont see a use for these two complxes it forms yet, but Im sure in time, they will resurface as the key feature of a new idea. All in good time...

                                                   PrimoPyro
Vivent Longtemps la Ruche!