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Author: Subject: Parared preparation
Mephisto
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[*] posted on 24-10-2005 at 00:58
Parared preparation


After my rather long abstinence from home-chemistry, I decided to perform a little preparation again. Because I don't have the right requirements for complex syntheses at home, I have chosen the easy preparation of Parared. It's an old dye-pigment, which was synthesized first in the year 1905. Today it isn't used anymore for dyeing textiles, as the molecule hasn't the necessary groups to be colourfast enough at the fibres. Parared is still used for low-cost inks, coloured pencils, detergents and polishes.

Another reason for this preparation was my wish to photograph a more or less attractive product. Beside this I had the necessary precursors and read a lot of interesting, historical texts about old fashioned dyes.

I prepared at first a diazonium salt by diazotizing 4-nitroaniline with sodium nitrite in hydrochloric acid. You can see the yellow diazonium salt suspension in the pictures 1-3. After this, a surplus of nitrous acid was destroyed with urea (see the positive nitrite test of iodide-starch paper in picture 4).
In another flask I dissolved 2-naphthol in a 2 N NaOH-solution (picture 5-6). By adding some drops of the diazonium salt to this solution the red dye was formed immediately (pic 7). The unstirred mixture has shown places of red pigment and not reacted and brown 2-naphthol (pic 8). After diluting, heating, filtering and almost dry sucking, the pigment was completely dried with silica gel and pulverised to become the nice bright red powder you can see in the last picture.

<table align="center" border="0" cellspacing="3" cellpadding="0" width="707" bgcolor="000000">
<tr>
<td align="center"><a href="http://www.lambdasyn.com/synfiles/pictures/pararot01-big.jpg" target="_blank"><img src="http://www.lambdasyn.com/synfiles/pictures/pararot01-thumb.jpg" width="173" height="130" border="0"</a></td>
<td align="center"><a href="http://www.lambdasyn.com/synfiles/pictures/pararot02-big.jpg" target="_blank"><img src="http://www.lambdasyn.com/synfiles/pictures/pararot02-thumb.jpg" width="173" height="130" border="0"</a></td>
<td align="center"><a href="http://www.lambdasyn.com/synfiles/pictures/pararot03-big.jpg" target="_blank"><img src="http://www.lambdasyn.com/synfiles/pictures/pararot03-thumb.jpg" width="173" height="130" border="0"</a></td>
<td align="center"><a href="http://www.lambdasyn.com/synfiles/pictures/pararot04-big.jpg" target="_blank"><img src="http://www.lambdasyn.com/synfiles/pictures/pararot04-thumb.jpg" width="173" height="130" border="0"</a></td>
</tr><tr>
<td align="center"><a href="http://www.lambdasyn.com/synfiles/pictures/pararot05-big.jpg" target="_blank"><img src="http://www.lambdasyn.com/synfiles/pictures/pararot05-thumb.jpg" width="173" height="130" border="0"</a></td>
<td align="center"><a href="http://www.lambdasyn.com/synfiles/pictures/pararot06-big.jpg" target="_blank"><img src="http://www.lambdasyn.com/synfiles/pictures/pararot06-thumb.jpg" width="173" height="130" border="0"</a></td>
<td align="center"><a href="http://www.lambdasyn.com/synfiles/pictures/pararot07-big.jpg" target="_blank"><img src="http://www.lambdasyn.com/synfiles/pictures/pararot07-thumb.jpg" width="173" height="130" border="0"</a></td>
<td align="center"><a href="http://www.lambdasyn.com/synfiles/pictures/pararot08-big.jpg" target="_blank"><img src="http://www.lambdasyn.com/synfiles/pictures/pararot08-thumb.jpg" width="173" height="130" border="0"</a></td>
</tr><tr>
<td align="center"><a href="http://www.lambdasyn.com/synfiles/pictures/pararot09-big.jpg" target="_blank"><img src="http://www.lambdasyn.com/synfiles/pictures/pararot09-thumb.jpg" width="173" height="130" border="0"</a></td>
<td align="center"><a href="http://www.lambdasyn.com/synfiles/pictures/pararot10-big.jpg" target="_blank"><img src="http://www.lambdasyn.com/synfiles/pictures/pararot10-thumb.jpg" width="173" height="130" border="0"</a></td>
<td align="center"><a href="http://www.lambdasyn.com/synfiles/pictures/pararot11-big.jpg" target="_blank"><img src="http://www.lambdasyn.com/synfiles/pictures/pararot11-thumb.jpg" width="173" height="130" border="0"</a></td>
<td align="center"><a href="http://www.lambdasyn.com/synfiles/pictures/pararot12-big.jpg" target="_blank"><img src="http://www.lambdasyn.com/synfiles/pictures/pararot12-thumb.jpg" width="173" height="130" border="0"</a></td>
</table>

By clicking on the pictures, they can be enlarged to a resolution of 1024x768 pixels.

People, who can read German might have a look to the synthesis-text on LambdaSyn.com, which I've uploaded this morning (here).

BTW: Although this was only done for fun, I wanted to profit from this by making my own red ink :D. But this didn't worked, as the product won't dissolved very much in solvents. So I couldn't prepare a deep-coloured Parared-solution to write or paint with it. Neither with ethanol or acetone nor with toluene. I don't know how this stuff can be used for industrially produced inks. Maybe as a colloid?

~Mephisto

Edit: I don't know the reason for that gap above the pictures (?), I've used just normal HMTL-code for tables.

[Edited on 24-10-2005 by Mephisto]




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leu
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[*] posted on 24-10-2005 at 05:12


From the Chemical Formulary:

Para Red inks were used most often for label and carton work due to their good permanence to light and excellent covering.

Label Red

No. 0 Lithographic Varnish 5 lbs
No. 1 Lithographic varnish 8 lbs
Medium Bodied Rosin
and Mineral oil Varnish 6 lbs
Para Red Dark Dry 6 lbs
Para Red Light Dry 2 lbs
Aluminum Hydrate Dry 8 lbs
Wool Grease 1 lb 8 oz
Cobalt Linoleum Drier 2 lbs
Wax Compound 8 oz
Barium Sulfate Dry 10 lbs

:)

[Edited on 24-10-2005 by leu]




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Sergei_Eisenstein
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[*] posted on 24-10-2005 at 06:10


Quote:
BTW: Although this was only done for fun, I wanted to profit from this by making my own red ink :D. But this didn't worked, as the product won't dissolved very much in solvents. So I couldn't prepare a deep-coloured Parared-solution to write or paint with it. Neither with ethanol or acetone nor with toluene. I don't know how this stuff can be used for industrially produced inks. Maybe as a colloid?



Hello,


A visually nice and interesting preparation! Concerning the ink, did you try NMP (N-methylpyrrolidone)? It is often used in printing inks. Ethers derived from (1,3- and 1,2-) propanediol and glycol are also used as a matrix.
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Mephisto
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[*] posted on 24-10-2005 at 10:46


I didn't try NMP as solvent, because I didn't have it at home. DMF is the most aprotic solvent, which I have around. At first I will try to dissolve the Parared again in toluene by heating it stronger under reflux. Than I'll give it a try with DMF. If both won't work, I hope to have the time to make some 1,4-dioxane. Thanks for your help, Sergei_Eisenstein!

~Mephisto




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Sergei_Eisenstein
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[*] posted on 26-10-2005 at 07:46


I'm trying to remember an ink analysis I've performed at school in the past, but it has been many years and the analysis was mainly focussed on the colourants and not the matrix. Colourants can be separated on TLC easily. Spots were screpad off and analyzed with a UV. It's a good exercise to get introduced in the world of TLC and UV.
I said NMP was used as matrix for printing inks, but I think it was N-methyl NMP instead.
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[*] posted on 26-10-2005 at 08:51


Very nice.
Mephisto, do you know if this reaction works i.e. with phenol? or i.e. aminophenol (obtained from paracetamol)?

I have to look up the principles of azocouplings...




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Mephisto
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[*] posted on 26-10-2005 at 10:57


Quote:
Originally posted by chemoleo
Very nice.
Mephisto, do you know if this reaction works i.e. with phenol? or i.e. aminophenol (obtained from paracetamol)?

I have to look up the principles of azocouplings...


Yes, the reaction works with phenol for sure. Every activating group at the aromatic ring makes an azocoupling possible. The reaction in my preparation above would give with phenol 4-(4-nitrophenylazo)-phenol, as the para product would be preferred. Other activating groups like the amino-groups will work too.

But I doubt you will get a nice coloured dye by preparing 4-(4-nitrophenylazo)-phenol or the 4-aminophenol analogue, because I didn't find any literature claiming their use as dye.

~Mephisto




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[*] posted on 29-11-2005 at 08:34


Mephisto,

May I suggest p-Dimethylaminoazobenzene, a.k.a. "Butter Yellow" the next time you do an azo dye synthesis? :D

sparky (~_~)




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[*] posted on 29-11-2005 at 23:08
aniline and azo dyes


The colors are beautiful and the experiment doesn't seem too difficult. Amazing result.

I have list of dates concerning the history of the early synthetic dyes and it says para-red was synthesized / commercially produced starting 1885. Thio-indigo red, the first "indigoid" was synthesized 1905 so maybe that's the one you are thinking of ?

Also there is some current health scare about para-red being a carcinogen being found in artificially colored foods. So it may not be the greatest stuff to get on your hands, etc.

I am trying to work out a related question on the aniline dyes in another thread, maybe we can work on the answer together.

It seems difficult in the case of this particular dye because the way they dyed the fabrics was to do the reaction on the fabric itself - put the fabric in the naphtol and then add the diazotized amine.

But there are some references to use of para-red as a printing ink so it must be easily soluble in something, if you could find the formula for one of those inks...

Maybe in the formula for some old printing inks because it has probably been banned now due to the carcinogenicity
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