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Azo Dyes

Page history last edited by jbfriesen 12 years, 8 months ago

The inspiration for this experiment is from: "A Combinatorial Experiment Suitable for Undergraduate Laboratories" by Benjamin W. Gung and Richard T. Taylor. Journal of Chemical Education, Vol 81, No. 11, November 2004.

Changes to published procedure

We doubled the quantities used in the JCE article.

Summary of Experiment

The 2.6% aqueous sodium carbonate solution was prepared ahead of time.

The first part was done in beakers and no test tubes.

In 2008, we used the 3 positional isomers of aminobenzenesulfonic acid with 1-naphthol, 2-napthol, and 1-bromo-2-napthol. The latter nucleophile was a new addition to the scheme.

In 2009 we substituted 1,5-dihydroxynaphthalene for 1-bromo-2-napthol which gave a strong odor of bromine when taken out of the fume hood. 1,5-dihydroxynaphthalene worked well.

IN 2011 we used the 3 positional isomers of aminobenzenesulfonic acid with 1-naphthol, 2-napthol, and 1-nitroso-2-naphthol. The latter nucleophile was a new addition to the scheme.

Student Handout for 2011

Student Handout for 2009

Positive

+This experiment goes well with the "reactions of benzene derivatives" chapter.

+ Its colorful. The multifabric strip is a unique analysis technique - a little variation from the characterization of a white solid by melting point.

+ I really like these combinatorial schemes where students can contrast and compare their products.

Neutral

±A precipitation is not really necessary in Part I.

±In Part II, a little additional concentrated HCl helps with the final precipitation.

±If the student does not get a precipitate, they use the colored solution as a dye bath in Part III.

±The 1-bromo-2-naphthol behaved well. Unfortunately it had a pretty strong bromine odor.

Negative

-It may be rather difficult to determine the actual structure of the products. Has this ever been done? Is it a mixture, or what?

Inquiry & Extension ideas

=Combinatorial schemes are always interesting to contrast and compare products.

=Could be incorporated with alot more information and discussion on the interactions between dyes and fabrics. Why do certain fabrics "hold" certain dyes?

=It is possible to vary the nucleophile (e.g. naphthol derivative). It may be possible to vary the sulfonilic acid too. Alot of possibilities!

=At one time in the past. used a study of chemical dyes as a semester-long project. There is so much chemistry history associated with the dying industry. There is also a whole field of natural dyes that can be explored.

=I ofen pair this up with a "Natural Dyes" lab where we dye the same multifiber strips that we use in the "Azo Dyes" lab. Natural Dyes.doc