Preparation of Para Red and Related Azo dyes

Purpose :
The purpose of this lab was to prepare two azo dyes, para red using a reaction of p-nitroaniline and 2-naphthol, and a related azo dye. Para dye is a chemical dye used in printing. It dyes cellulose fabrics to red.


[reaction diagram for the other azo dye is missing]

Result:
The reaction yielded the desired product, para red, a red colored dye with the use of p-nitroaniline and 2-naphthol.
The second reaction with p-anisidine and 1-naphthol yielded a darker red colored azo dye solution.

Discussion :
The first synthesis using the ketone, 2-napthol, and aldehyde,nitroaniline, produced a red colored para red solution while the other reaction with p-anisidine and 1-naphthol produced a darker red colored solution. The difference in colors of both azo dye was because of the difference in the attachment of the hydroxyl group to the compound. 1-naphthal contains a hydroxyl group on the first carbon, ortho to the attached benzo group while 1-naphthol contains a hydroxyl group on it’s second carbon, meta to the attached benzo group. The difference in color change can also been as a result of the aldehydes used in the solutions.

Conclusion:
The synthesis of para red , and a similar azo dye were achieved through the experimental procedures undertaken, and the products were similar to the predicted azo dyes. The use of similar molecules with different hydroxyl positions reflected on the end result of the solution. However, this experiment may still be improved by careful division of the solutions prior to mixing both solutions because the experiment is skewed if too much of one carbonyl compound is added to the other.