Diazotization reactions

[Summ]

Hi,

I was wondering if anyone can help me understanding how these reactions work.

What is happening by adding CuSO₄-5H₂O, [NH₄₊][OH^-] and HONH₂-HCl (hydroxylammonium chloride) together in an aqueous solution? Is it forming a diazonium salt solution?

And when we are mixing the above solution with another diazonium salt [(HO-Benzenering-N-=-N-⁺)(Cl^-)] in a diethyl ether solution what product are we expected to have? Will be azo coupling reaction occurred?

I am trying to synthesize a dihydroxyazobenzene and I found this synthetic procedure from a patent.

Any idea will be well accepted and appreciated!!

Thank you in advance!

[Knumbnuts]

Usually one uses sodium nitrite to form the diazonium salt, you don't sen to have that in your mixture.

From your mixture I won't expect any reaction except perhaps the hydroxylamine coordinating to the copper.

[John Cuthber]

It looks very strange to me. Can you post a link to the patent?

[Summ]

For the synthesis of this diazonium salt [(HO-Benzenering-N-=-N-⁺)(Cl^-)] they used sodium nitrite, aminophenol and HCl. I don't understand their next step. How they formed the product with the rest chemicals.

I found this experimental procedure from scifinder for the synthesis of 4,4' dihydroxyazobenzene.

(it's not well explained or written)

 

In a 1 L beaker, p-aminophenol ( 18 mmol) will be added and made aqueous by adding water 20.00 ml. Then, hydrochloric acid 7 ml and water 29 ml will be added dropwise over 30 minutes. Then, 1.3 g sodium nitrite will be dissolved in water (100.00 ml, 18 mmol) and the aqueous solution of the hydrochloride will be slowly added for 2 hours. The above operations will be carried out at 0~3 °C.

Into another beaker, copper(II) sulfate pentahydrate (33 mmol), ammonia water ( 29.00 mmol) and hydroxylammonium chloride ( 18 mmol) will be added, then dissolved in 18 ml water to form the diazonium salt solution. To this aqueous solution of diazonium salt, the above prepared diazotized solution will be added dropwise. Then, 18.00 ml diethyl ether will be added and coupling reaction will be carried out. After the completion of the reaction, filtered, washed with dilute hydrochloric acid solution and crude product will be obtained.

 

Yoshino N., Kondo Y., Kawaharatsuka M., Gemini-type fluorohydrocarbon chain-introduced surfactants having azobenzene-based spacers and their preparation, Jpn. Kokai Tokkyo Koho, 2009149601, 2009

 

I will try to download the patent and translate it from Chinese.

Thanks!!

Edited June 5, 2013 by Summ

[Summ]

For the synthesis of this diazonium salt [(HO-Benzenering-N-=-N-⁺)(Cl^-)] they used sodium nitrite, aminophenol and HCl. I don't understand their next step. How they formed the product with the rest chemicals.

I found this experimental procedure from scifinder for the synthesis of 4,4' dihydroxyazobenzene.

(it's not well explained or written)

 

In a 1 L beaker, p-aminophenol ( 18 mmol) will be added and made aqueous by adding water 20.00 ml. Then, hydrochloric acid 7 ml and water 29 ml will be added dropwise over 30 minutes. Then, 1.3 g sodium nitrite will be dissolved in water (100.00 ml, 18 mmol) and the aqueous solution of the hydrochloride will be slowly added for 2 hours. The above operations will be carried out at 0~3 °C.

Into another beaker, copper(II) sulfate pentahydrate (33 mmol), ammonia water ( 29.00 mmol) and hydroxylammonium chloride ( 18 mmol) will be added, then dissolved in 18 ml water to form the diazonium salt solution. To this aqueous solution of diazonium salt, the above prepared diazotized solution will be added dropwise. Then, 18.00 ml diethyl ether will be added and coupling reaction will be carried out. After the completion of the reaction, filtered, washed with dilute hydrochloric acid solution and crude product will be obtained.

 

Yoshino N., Kondo Y., Kawaharatsuka M., Gemini-type fluorohydrocarbon chain-introduced surfactants having azobenzene-based spacers and their preparation, Jpn. Kokai Tokkyo Koho, 2009149601, 2009

 

I will try to download the patent and translate it from Chinese.

Thanks!!

I found another paper with the same procedure.

https://www.jstage.jst.go.jp/article/jos/59/3/59_3_151/_pdf

 

" 2.3.1 Synthesis of intermediate (3)

To a mixture of p -aminophenol (2.0 g, 18.3 mmol) in 20 ml

of water, 3 mM HCl aqueous solution (30.3 ml) was added

dropwise over 30 min at rt; an aqueous solution (108 mL) of

NaNO

2

(1.3 g, 18.8 mmol) was then slowly added over 120 min at 0°C

. The reaction mixture was added dropwise to an

aqueous solution consisting of water (18.3 mL), CuSO4･5H2O (8.2 g, 32.8 mmol), 28% NH

3

(5.5 mL), and hydroxyammonium chloride (1.3 g, 8.3 mmol). The reaction mixture

was filtered, and the crude product was then washed with 1 M HCl. Product 3

was obtained as a yellow solid when

the crude product was recrystallized from a mixed ace-

tone/water solvent. The yield was 1.4 g (71%). "

[Knumbnuts]

They made a solution of the diazonium salt.

They made a solution of copper sulphate in ammonia with hydroxyl amine, which they then added to the diazonium salt solution.

They then added ether and let the reaction proceed.

[Summ]

I understand what solutions I have to make and how to conduct the experiment. It is also clear for me the diazotization at the first step but I cannot understand the reaction mechanism of the azo coupling with these reagents.

[John Cuthber]

This

copper(II) sulfate pentahydrate (33 mmol), ammonia water ( 29.00 mmol) and hydroxylammonium chloride ( 18 mmol)

will give a solution/ suspension of CuCl in ammonia solution.

 

I think the next steps are probably something like Cu+ catalysed decomposition of the diazonium ion to the phenyl cation. then coupling with the rest of the diazonium salt. (i'm guessing at a radical reaction here, given the paired oxidation states of Cu+ and Cu++)

[Summ]

Thank you very much!!