Martius yellow synthesis


Synthesize a dye, in this case Martius yellow (or acid yellow 24) by indirect nitration of α-naphthol (1-naphthol), to obtain the dinitrated compound. This is successive sulfonation and nitration reactions. In addition, form the salt of the dinitrated compound with ammonium hydroxide to obtain the aforementioned dye.

synthesis martius yellow dye 1-naphthol 2,4-dinitro-1-naphthol nitration sulfonation hydroxylamine ammonium salt XTWUZSGBAZWJJK-UHFFFAOYSA-N


Martius yellow dye was discovered in 1868 by Karen Alexander Von Martius. And its chemical structure consists of the ammonium salt of 2,4-dinitro-1-naphthol. Its most frequent use is as a mothproof dye for wool. With 1 g of Martius yellow dye 200 g of wool can be dyed.

Diazonium salts are relatively stable, and can be formed with aromatic primary amines by reaction with nitrous acid. These salts, in turn, can act as weak electrophiles and react with activated aromatic rings, producing electrophilic aromatic substitution reactions (SEAr). Phenols and aromatic amines have activated aromatic rings, and this allows them to react with diazonium salts. This produces a number of compounds that are used as dyes.

The synthesis is carried out by aromatic sulfonation of α-naphthol (1-naphthol) with concentrated sulfuric acid. Subsequently, an ipso nitration of the previously obtained disulfonic acid is carried out with a mixture of nitric acid and sulfuric acid in aqueous medium. In this way, the exchange of functional groups occurs easily.

Experimental procedure

a) Synthesis of 2,4-dinitro-1-naphthol

2.5 g of 1-naphthol are placed in an Erlenmeyer of 100 ml and 5 ml of concentrated sulfuric acid (H2SO4) are added. A water bath is prepared. The mixture is heated (at a temperature of 37-40 °C) for approximately 10 min and stirred on a hot plate with magnetic stirring until dissolution and disappearance of the red color.

Once the process is finished, it is left to cool in an ice bath, and 15 ml of ice water is added through the walls of the Erlenmeyer and it is left to rest for 2 min.

Another beaker is prepared with 4 ml of concentrated nitric acid (HNO3) in an ice bath. And they are added to the reaction crude of the previous stage drop by drop. The mixture is left to stand for 2 min. Then the reaction crude is heated in a water bath (at 37 ºC) for 5 min.

Once the process is finished, the product separates as a yellow paste, which is poured into another beaker with approximately 30 ml water/10 g crushed ice to break up the paste formed.

The product is collected by vacuum filtration and washed with cold water.

b) Obtaining the ammonium salt of 2,4-dinitro-1-naphthol

The third reaction is carried out in another beaker. Add 75 mL of hot water and 2.5 mL of concentrated ammonium hydroxide, heat to boiling point, and stir (magnetic stirring) to dissolve the solid. Add 5 g of ammonium chloride (NH4Cl) to the reaction crude to obtain the ammonium salt (Martius Yellow). Finally, cool in an ice bath, and vacuum filter the Martius Yellow dye and wash with water containing 1-2 % ammonium chloride, and collect the product obtained (b.p. 144-145 °C). It is allowed to dry and the yield is calculated.

International Chemical Identifier

The IUPAC InChI key identifiers for the main compounds used in this experiment are provided to facilitate the nomenclature and formulation of chemical compounds and the search for information on the Internet for these compounds.

4-hydroxynaphthalene-1,3-disulfonic acidGMSFXHLBYYCMAT-UHFFFAOYSA-N

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