19
votes
Accepted
Mechanism of formation of 2-naphthol red dye (aka Sudan 1)
The most important thing to point out here is that your arrows are backwards. The diazonium is not the nucleophile. It is the electrophile. The diazonium ion has one lone pair. If it were a ...
- 17.5k
14
votes
Accepted
Looking for a dye which emits around 680 nm
There are two dyes commonly used in biochemistry research with $\lambda_\mathrm{Ex}$ of around $\pu{650 nm}$. They are Alexa Fluor 647 from ThermoFisher and Cyanine5 (Cy5) from Lumiprobe. Two example ...
- 41.1k
11
votes
Anthracine blue composition
Springmühl indeed reported Anthracene Blue (orig. "Anthracenblau" (German)) from an intermediate with brutto-formula $\ce{C14H7O3}$. It seems like this method only worked well at a lab scale....
- 38.4k
10
votes
Mechanism of formation of 2-naphthol red dye (aka Sudan 1)
The formation of para-red is an example of electrophilic aromatic substitution.
The electrophile reacts with the ring carbon that is ortho to
both the activating group ($\ce{-OH}$) and the other ...
- 5,511
7
votes
Do indigo and leuco-indigo have fully conjugated pi systems?
Let's just start with stating the very obvious: Figure 2.23 has more errors than there should be in an entire chapter.
Indigo
With the exception of bonds to hydrogen, all other bonds are nicely ...
- 44.3k
6
votes
Has anyone added dyes to a mixture about to separated by chromatography in order to visualize where the desired product lies?
the idea is good for academic purposes and good for a lecture hall demo. One may also try a UV lamp, if your compound fluoresces in the column. Caution UV is very harmful for the eyes (protective ...
- 42.2k
5
votes
Strange green and gold coloured chemical
I worked for a time with squaraine dyes that were often greenish in the crystalline state, but ink-blue when in solution.
However, I would suggest that you take an analytical approach to identifying ...
- 1,158
4
votes
How to make equal density pool dye without diffusion
Whole milk with food coloring solved my problem. Whole milk has a specific gravity of 1.01, which allowed it to settle to the bottom around the main drains. The diffusion rate was extremely slow ...
- 191
4
votes
What replaced lead-based pigments?
Into the 70's the better white paints were tri-metal; lead, zinc and tin (oxides). Titanium oxide (rutile) replaced the lead and the zinc and tin adjusted. The titanium has excellent hiding power so ...
- 3,777
3
votes
Accepted
Indigo and the Environment: is it that bad?
For this process, sodium dithionite (Na2S2O4) has been considered as a best reducing agent in traditional and industrial dying but the reducing agent releases sodium sulphate, sulphite and ...
- 42.2k
3
votes
Accepted
Choosing a transition metal catalyst instead of iron catalyst to investigate the degradation of methyl orange?
According to Ref.1:
In recent research, nickel oxide nanoparticles have drawn a greater interest, because of its unique properties. It belongs to a wide band gap $(3.6–\pu{4.0 eV})$ p-type ...
- 41.1k
3
votes
Azo dyes with different colours than Yellow, Orange and Red
Wikipedia article Category:Azo dyes list you all the azo dyes in the
whole color spectrum, with colors explicitly indicated (yellow, orange, brown, red, blue, black) in the names of some of the dyes. ...
- 26.4k
2
votes
Choosing a transition metal catalyst instead of iron catalyst to investigate the degradation of methyl orange?
Iron will not form sludges at low pH.
However, how do I go about choosing the transition metal catalyst for
my project. Which transition metal would be the most suitable and why?
If you are thinking ...
- 42.2k
2
votes
Does there exist a dye that will primarily bind with water in a water/oil emulsion?
You are asking for water-soluble dyes. Typical applications are dyeing methods in microscopy and food coloring.
Water-soluble dyes for microscopy: e.g. Eosin Y, Methylene Blue, Ethyl Green.
See also ...
- 295
2
votes
Accepted
Why does SYBR green emit more signal when bound to DNA?
In dyes such as this rotation about bonds that can be involved in the conjugated part of the molecule contribute to radiationless transitions causing the excited state to transfer its energy to a ...
- 30.9k
2
votes
Do indigo and leuco-indigo have fully conjugated pi systems?
Concerning this part of your question:
I also want to ask about why leucoindigo isn't planar. According to
Wikipedia, "In indigo white, the conjugation is interrupted because
the molecule is ...
- 1,735
2
votes
Accepted
Azo dyes with different colours than Yellow, Orange and Red
More complex azo dyes can be other colors, as with trypan blue. With its more complex structure comes more extended conjugation, which shifts visible light absorption from the shorter violet and blue ...
- 61k
2
votes
Accepted
Why don't universal indicator solutions react with themselves?
In a solution containing multiple species that undergo acid/base chemistry, everything will react with everything (including water, which can act as acid or as base). Equilibrium is established ...
- 41.3k
2
votes
Looking for a non-toxic, environmentally safe highly colored or intense dye
Many organic dyes which are fluorescent can be carcinogenic like the famous Rhodamine dyes. You can try a couple of tricks. One of best inks, at least for demonstrations, is the yellow highlighter's ...
- 42.2k
1
vote
Accepted
Which compounds react positively in the aniline dye test?
First, the aniline is converted to a diazonium halide salt in the presence of acid and sodium nitrite, per this reference.
Then, the diazonium salt reacts with the phenol to give an azo compound, per ...
- 700
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