Dear Yossef

Please, find in attach, a paper on: Synthesis of Some Novel Antibacterial Sulfonamide Reactive Dyes.

In this paper you'll find:

Diazotization of Sulfonamide:

The sulfonamide (0.01 mole) was stirred in hydrochloric acid (6 ml), the mixture was gradually heated up to 70˚C, till clear solution obtained then the solution was gradually cooled to 0–5˚C in an ice bath, a solution of sodium nitrite (0.01 mole) in water (4 ml), previously cooled to 0˚C, was then added over a period of 15 min with

stirring the stirring was continuous for half an hour, the clear diazo solution at 0– 5˚C was used for subsequent coupling reaction.

2.5. Coupling of the sulfonamide diazonium salt with the coupling component:

To an ice cold and stirred solution of the coupling component (0.01 mol), a freshly prepared diazo solution (0.01 mole) was added drop-wise over a period of 15 min, the pH was maintained at 7.5–8.5 by simultaneous addition of sodium carbonate solution (20% w/v), the stirring was continued for 3 h, maintaining the temperature

below 5˚C, the pH was adjusted to about 6.8.

The reaction mixture was reach to room temperature and sodium chloride (15%) of the total solution used added during a period of half an hour, then the solution was cooled to 0–5˚C in an ice bath, the stirring was continuous for half an hour, remain overnight, filtered and dried at 40˚C under vacuum.

Dear Youssef,

Coupling reactions of diazonium ions

1-The reaction with phenol

Phenol is dissolved in sodium hydroxide solution to give a solution of sodium phenoxide.

The solution is cooled in ice, and cold benzenediazonium chloride solution is added. There is a reaction between the diazonium ion and the phenoxide ion and a yellow-orange solution or precipitate is formed.

The product is one of the simplest of what are known as azo compounds, in which two benzene rings are linked by a nitrogen bridge.

For an illustration of the reactions, please use the following link:

http://www.chemguide.co.uk/organicprops/aniline/propsdiazo.html

2-The reaction with naphthalen-2-ol

Naphthalen-2-ol is also known as 2-naphthol or beta-naphthol. It contains an -OH group attached to a naphthalene molecule rather than to a simple benzene ring. Naphthalene has two benzene rings fused together.

The reaction is done under exactly the same conditions as with phenol. The naphthalen-2-ol is dissolved in sodium hydroxide solution to produce an ion just like the phenol one. This solution is cooled and mixed with the benzenediazonium chloride solution.

An intense orange-red precipitate is formed - another azo compound.

For an illustration of the reactions, please use the following link:

http://www.chemguide.co.uk/organicprops/aniline/propsdiazo.html

3-The reaction with phenylamine (aniline)

Some liquid phenylamine is added to a cold solution of benzenediazonium chloride, and the mixture is shaken vigorously. A yellow solid is produced.

 For an illustration of the reactions, please use the following link:

http://www.chemguide.co.uk/organicprops/aniline/propsdiazo.html

These strongly coloured azo compounds are frequently used as dyes known as azo dyes. The one made from phenylamine (aniline) is known as "aniline yellow" (amongst many other things - see note above).

Azo compounds account for more than half of modern dyes.

For more on this kind of reactions, please use the following link:

http://www.chemguide.co.uk/organicprops/aniline/propsdiazo.html

Hoping this will be helpful,

Rafik

Most importantly the temperature is very important factor in diazo coupling reactions. Diazonium salt is prepared by dissolving amine into hydrochloric acid and a cooled to 0-50C.A cooled aqueous solution of sodium nitrite (equivalent ) was added dropwise with stirring at such a rate so that temperature may not exceed  above 50C. The  diazonium salt thus obtained was  treated with aromatic amine or phenol at low 0-50C with stirring . The coloured azo dye precipitated  was  filtered. 

2,6-bis((E)-(2-hydroxynaphthalen-1-yl)diazenyl)-1-substitutephenyl-1,4-dihydropyridine-3,5-dicarbaldehyde (3)

Solution A was prepared by mixing 1 (0.01 mol) with concentrated HCl (6 mL) and water (6 mL) and cooling at a temperature below 5 °C in an ice bath. NaNO2 (0.02 mol) was dissolved in water (20 mL) at 5 °C to obtain solution B. Then solution A was added dropwise to solution B at 5 °C with stirring. The mixture was then slowly added into the solution of 2-napthol 2 (0.02 mol), which was dissolved in 10% NaOH (40 mL) at 5 °C. The mixture was kept chilled in the ice bath and stirred continuously for 10 min (Scheme 1). The precipitate 3 formed was filtered and recrystallized from glacial acetic acid, and washed with methanol and finally dried in a vacuum oven at 70 °C for 12 hours.

We made hydrazones by treating diazonium salts with malonic esters. These reactions were also applied in Laura Sereni's synthesis of cinnolines on my Research Gate page. The phenyl hydrazones made this way should not be nitrated as it will form picric acid.

I would like to couple in pH 5--7 diazo salt (stable in room temperature) with phenol to obtain green dye, any ideas?