Multi-Step Procedure for the Synthesis of Para-Red Dye

Running head: LAB REPORT 1

Lab Report


The experiment performed was a multiple-step procedure to synthesize para red dye. Due to time constraints, the multiple-step procedure was ended at the synthesis of p-Nitroaniline. The processes involved the synthesis of acetanilide from aniline and acetic anhydride, the synthesis of p-Nitroacetanilide from acetanilide, and the synthesis of p-Nitroaniline from p-Nitroacetanilide. The final product, p-Nitroaniline, was found to weigh 1.5629 grams. This is a 39.2 percent yield from the theoretical yield of 3.99 grams.


Aniline is a material with a great many uses. Products such as agricultural chemicals, antioxidants, polyurethane foam, and others are synthesized from this starting material.1 Para red dye, a red dye used in printing, is one such product.2Para red dye is banned from use in food in the United Kingdom as it is a potential genotoxic carcinogen.2This experiment follows a multiple step procedure for synthesizing para red dye, but stops at an intermediate product, p-Nitroaniline, due to time constraints for the experiment.

Percentage yield = (Actual/Theoretical) x 100
1.5629/3.99 x100
Data and Calculations
Theoretical Yield Calculations

Percent Yield Calculations

Total Yield
(0.6901x 0.392) x 100%= 27.05%

The product of the first extraction was acetanilide. This product looks white and very crystal-like and it had no odor to it. We recovered 5.01 g on this first extraction, which is 69.01 % of the theoretical yield of 7.26 g. After this, this product was used to perform a second extraction to obtain p-Nitroaniline as the final product. The mass recovered in this second part was 1.5629 g which is only 39.2 % of the theoretical yield of 3.99 g. This product was yellow in appearance and it was also odorless. Dues to these physical attributes, it is safe to assume that the product obtained was in fact p-Nitroaniline, and while there might have been some impurities, an NRM was not performed to be able to observe such impurities.
A source of error for the weight of the final product may be the inability to completely remove the p-Nitroaniline or the acetanilide from their respective drying agents, causing a reduction in mass. Another possible reduction in the mass of the final product could have arisen during either one of the 2 extractions. Some of the organic solution could have remained in the separatory funnel after draining, becoming lost when the non-organic layer was removed. Furthermore, some of the product could have been lost when transferring it to the flasks for the extraction process. In the future, steps should be taken to minimize these losses to obtain more methyl salicylate.
Synthesis of an azo dye needs two key components, the diazonium salt and the ?-bond rich coupling compound. A general synthesis of azo dyes can be seen in Figure 2 using ?-naphthol and an ayrl diazonium salt.

Azo Dye Synthesis (Al-Rubaie)

The hydroxyl group on ?-naphthol is an electron donating group which allows it to act as a ortho-, para-director. Unless the position is occupied the aryl diazonium will be attached pare. In case para is fully occupied, the aryl diazonium will attach to the para position.
Since this is a multi-step reaction, there are several possible sources of error. The first one would be during the recrystallization to obtain p-nitroacetanilide, it is possible that the solution was not properly chilled to completely obtain only the para product. there is also the use of too much SO4.
Synthesis of a diaznoium salt was performed beginning with aniline and creating p-nitroaniline. The diazonium salt reacted with ?-naphthol to create the final product of Dye Para Red. Melting point analyses were performed for acetanilide and the Dye Para Red.


1. Agency for Toxic Substances and Disease Registry. Aniline internet. CDC; 2011 (accessed 30 November 2016). Available from:
2. The National Archives. Para red dye internet. GOV.UK; Richmond, UK. 2011 (accessed 30 November 2016). Available from:

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Multi-Step Procedure for the Synthesis of Para-Red Dye. (2022, Feb 03). Retrieved from

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