2,4-DinitrophenylHydrazine Synthesis [Lab Report]

Synthesis of 2,4-Dinitrochlorobenzene



First a Sulfo-Nitric solution was prepared by carefully mixing 30mL of sulfuric acid [1,8 g/mL] and 14,5 mL of azeotropic nitric acid, then the solution was left to cool.
With vigorous stirring, to the sulfo-nitric mixture, 8mL of Chlorobenzene were added by portions, not letting the temperature go above 50ºC. Once all the chlorobenzene was added the mixture was heated to 95ºC and maintain for 2hs with stirring.
After the 2hs passed, to the solution, 150mL of water were added and stirred, the mixture separates in 2 layers. The organic phase was washed with water 3 times.
Crud Yield 13,01g [81,4%]



Synthesis of 2,4-Dinitrophenyl hydrazine.



These syntheses requires the preparation of a Hydrazine free-base solution.

Preparation of Free-base Hydrazine solution:

On a beaker, 7g of Hydrazine sulfate and 25mL of water were mixed, and the mixture was heated to boiling. Once boiling was observed, the heat was turned down and 15g of anhydrous sodium acetate were added in portions. Once all the acetate was added the solution was left hot for 5min and then 15mL of ethanol were added and the mixture filtered, with the filtered washed twice with hot ethanol. The solution was stored for immediate use.

2,4-Dinitrophenylhydrazine:

On an Erlenmeyer flask with ground glass joint, 10g of 2,4-Dinitro-chlorobenzene were dissolved in 50mL of 95% Ethanol, to which the hydrazine solution is added. The mixture is left to reflux for 1 ½ Hs.
The mixture was then cooled, filtered, and the precipitated product recrystallized with butanol [30mL per gram of 2,4-Dinitrophenylhydrazine]
Yield: 4.03g [41,2% based on Dinitrochlorobenzene]



Source: http://www.orgsyn.org/demo.aspx?prep=CV2P0228

Funny enough, I actually just used some as a stain today! It’s especially useful when, as in my example, the starting material and the product have the same Rf and are thus indistinguishable by UV visualization alone:

Thanks Charley1957 and Fery.

Yup, i use these compound to make Brady's Reagent and identify Ketones and Aldehydes

Nice TLC method there Texium, i haven't heard of that one before.

[Edited on 1-3-2023 by Chem Science]

Quote: Originally posted by Chem Science

Yup, i use these compound to make Brady's Reagent and identify Ketones and Aldehydes Nice TLC method there Texium, i haven't heard of that one before.