1. DYES Dr. Sheppard, CHEM 4201, Fall 2014

2. Dyes in Food  Food Coloring  Natural colors  Synthetic dyes  Why add food coloring ?  Regulation  Structure

3. Mauve  Perkin’s idea:  Mauveine

4. Types of Synthetic Dyes  Triphenylmethyl  Azo

5. Triphenylmethyl Dyes  Pararosaniline, malachite green, crystal violet

6. Azo Dyes  Aniline Yellow  Bismarck Brown

7. Azo Dyes  Methyl orange  Orange II  Para red  Amaranth red

8. Azo Dyes  Preparation:  Diazonium salt (Ar-N 2 + )and activated aromatic compound  Diazotization step  Coupling step

9. In-class Assignment  Draw a mechanism for the coupling of aniline with a diazonium ion. Pay close attention to regiochemistry (i.e. will the coupling occur ortho, meta, or para?)  Draw the two aromatic compounds that would be used to synthesize Para red.

10. Dyeing  Natural dyes vs. synthetic dyes  Fastness  Levelness  Fabric/fiber

11. Direct Dyeing malachite green

12. Direct Dyeing Congo red

13. Ingrain Dyeing

14. Mordant Dyes tannic acid

15. Vat Dyes

16. Disperse Dyes

17. Fiber-reactive Dyes