Sciencemadness Discussion Board

OTC cyanamides?

Polverone - 6-7-2003 at 21:04

This looks interesting, as cyanamides may lead to other compounds, guanidine nitrate among them:

Patent GB710143
http://l2.espacenet.com/espacenet/viewer?PN=GB359652&CY=...

Looks nicer than constructing your own arc furnace.

Edit:

Looks like this is actually a well-known process. Ullmann says:

Calcium cyanamide was probably first obtained in the laboratory in 1877 by heating calcium carbamate to red heat [3]. In 1889 it was prepared in larger quantities by heating thoroughly mixed, finely pulverized urea and calcium oxide [4].

[3] E. Drechsel, J. Prakt. Chem. 16 (1877) 180 – 200. [4].

[4] F. Emich, Monatsh. Chem. 10 (1889) 321 – 352.

IIRC, ethyl carbamate can be formed simply by boiling urea with ethanol. Reaction with Ca(OH)<sub>2</sub> should yield calcium carbamate.

[Edited on 7-7-2003 by Polverone]

chemoleo - 3-3-2005 at 14:59

I found this interesting entry in Ashfords Dictionary of Ind. Chemistry:
Quote:
lead cyanamide
PbNCN (247.22).
Yellow pigment. d: 6.8 kg/l. Slightly
soluble in water forming alkaline solutions. Its use in paint is controlled in many countries.
Uses:
anticorrosion pigment (primer paints)
Production
• lead acetate + cyanamide (salt formation)
Derivatives
N-cyanoimido-S,S-dimethyldithiocarbamate


Now, has anyone ever seen lead cyanamide as anticorrosion primers or paint? I haven't but felt it's worth asking, as I am sure the cyanamide could be extraced from it!

lead cyanamide

Rosco Bodine - 22-3-2007 at 15:15

I haven't seen it , lead based paint pigments are pretty much gone from use , unless there is some special case use where no substitute would work .

The lead cyanamide was used as a anti-fouling paint
on the bottoms of boats , as marine barnacles will not
attach , grow and accumulate on the toxic lead cyanamide
paint or its slowly hydrolysing surface . I would suppose it is very very slightly soluble and eroded very slowly in water like most of the toxic anti-fouling paints .

There were also some mercury based anti-fouling paints
used at one time , but I believe they are pretty much
out of use also .

Copper and chromium based anti-fouling paints are
what is used presently .

Regarding the cyanamide , from what references I have read , the calcium acid cyanurate is probably a better starting point , than mixing urea and lime ....since it
eliminates the vapor - solid phase mixture reaction stages
which are incomplete and need fluidized beds and higher temperatures , while not producing as high a yield or as pure a product . The urea method proceeds through
the cyanurate as an intermediate , therefore simply using the preformed cyanurate in pure form should skip over
that inefficient reaction stage of the urea process .

Urea may be rapidly decomposed converted to cyanuric acid
in 85% yield by heating with ammonium chloride
( US2527316 ) , and then the pure calcium cyanurate
can be made and isolated separately . Thermal decomposition of the calcium acid cyanurate at ~350C should
first give the normal calcium cyanate , with evolution of
cyanic acid , and upon further heating above 500C the calcium cyanate should decompose with evolution of CO2 , leaving the pure calcium cyanamide .

Attached is a patent process US2213441 for lead cyanamide yellow paint pigment , produced from calcium cyanamide . Some of the examples provide free acid cyanamide and sodium acid cyanamide as an intermediate which could be used for producing other different end products than lead cyanamide .

Attachment: US2213441 Free Acid Cyanamide , Sodium Acid Cyanamide from Calcium Cyanamide.pdf (366kB)
This file has been downloaded 1193 times

Engager - 3-8-2010 at 12:03

Preparation of calcium cyanamide from urea and calcium carbonate.


[Edited on 8-3-2010 by Polverone]

Picric-A - 3-8-2010 at 12:30

Quote: Originally posted by Polverone  

IIRC, ethyl carbamate can be formed simply by boiling urea with ethanol. Reaction with Ca(OH)<sub>2</sub> should yield calcium carbamate.

[Edited on 7-7-2003 by Polverone]


Ethyl carbamate only forms very slowly by the reaction between ethanol and urea at rtp.

A more efficient/ quicker method is the reaction between urea nitate and ethanol, which IRRC produces quantitive yields.