Sciencemadness Discussion Board

Lead (II) thiocyanate

Random - 7-5-2011 at 06:57

I need some lead (II) thiocyanate for making nitriles like benzonitrile by this procedure:

(RCOO)2Zn + Pb(SCN)2 = 2 RCN + ZnS + PbS + 2 CO2

I would use zinc benzoate and lead (II) thiocyanate for the reaction, but I have problem with obtaining any thiocyanate salts. I need to make one by myself and there is a problem.

I have some prussian blue temperas, maybe I could make potassium and sodium ferrocyanides by mixing prussian blue with sodium bicarbonate or carbonate? How could I substitute sulfur for that iron to make thiocyanate ion? Maybe there is alternative route to that thiocyanate ion?

I have no option of buying it.

kicsiatom - 7-5-2011 at 08:38

Can u buy ammonium tiocyanate (ammonium rodanide)?

This is important analytical chemical.

DJF90 - 7-5-2011 at 09:00

Do you have a reference for that reaction?

Random - 7-5-2011 at 15:46

I am not buying things online and there is no store selling it here.

DJF90, http://www.erowid.org/archive/rhodium/chemistry/ketamine2.ht...

Check that nitrile synthesis. While I am not definitely interested in drug synthesis, this is interesting route to nitriles.

I actually need benzonitrile to make p-hydroxybenzaldehyde from it :D

kmno4 - 7-5-2011 at 21:44

Quote: Originally posted by DJF90  
Do you have a reference for that reaction?

Code:
http://dx.doi.org/10.1021/cr60132a001

Evilblaze - 11-5-2011 at 17:52

Quote:

Lead thiocyanate was prepared by precipitation from leadnitrate and ammonium thiocyanate. The precipitated salt was well washed with water, and twice with alcohol. The air-dried salt was further dried in an air-bath at 120'. The salt is pure white but turns somewhat yellow on long keeping. It blackens somewhat when dried in the air-bath.

-from J. Am. Chem. Soc., 1916, 38 (10), pp 2120–2128 (what kmno4 mentioned in the previous post).

Ammonium thiocyanate is made from the following reaction (because CS2 is highly toxic, extremely flammable and has a really bad odor, this is not an easy garage-chemistry experiment):
CS2 + 2 NH3(aq) → NH2C(=S)SNH4 → NH4SCN + H2S

Or, as it was previously mentioned ammonium thiocyanate could be bought as a commercial reagent.

smuv - 12-5-2011 at 07:28

With all the time it takes you to make Pb(SCN)2 you could just dehydrate benzamide, which by your posts in other threads, you have apparently made.

UnintentionalChaos - 12-5-2011 at 14:38

Quote: Originally posted by Random  
I actually need benzonitrile to make p-hydroxybenzaldehyde from it :D


I've been over this whole sequence in theory already. IIRC, p-hydroxybenzoic acid gives nothing of value on fusion with lead thiocyanate. However, fusion of p-hydroxybenzamide with ammonium sulfamate gives ~25% yield of the corresponding nitrile, which can be reduced with SnCl2/HCl in dry ether (Stephen reduction) to the aldehyde. A much higher yield of the nitrile can be obtained, but the procedure calls for a lot of Ac2O. The p-hydroxybenzamide can be made by ammonolysis of a paraben preservative. IIRC a guy on ebay sells methylparaben by the pound for a reasonable price. If you are feeling rather mad, p-hydroxybenzoic acid can be made from salicylic acid inefficiently by the orgsyn procedure (or supposedly more efficiently by a patent procedure). Fusion with urea per http://www.sciencemadness.org/talk/viewthread.php?tid=4201 will yield the amide.

I have papers somewhere...give me some time to find them all.

EDIT:

I can't seem to find the reference about hydroxy and amine-bearing benzoic acids giving negligible yield, but here's the rest...

p-hydroxybenzoic acid (orgsyn): http://orgsyn.org/orgsyn/orgsyn/prepcontent.asp?print=1&...
P-hydroxybenzoic acid (patent): http://tinyurl.com/3d78d5l
Additional Lett's nitrile synthesis info (see part I): http://books.google.com/books?id=UzzPAAAAMAAJ


[Edited on 5-13-11 by UnintentionalChaos]

Attachment: Substituted Benzaldehydes via Stephen Reduction.pdf (254kB)
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[Edited on 5-13-11 by UnintentionalChaos]

Attachment: nitrilesviaammoniumsulfamate.pdf (349kB)
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