Synthesis of an azo dye lab report

Synthesis of an Azo Dye Activity Azo dyes are one of the most common types of dyes used today. They are used as dyes for clothing, food coloring, and as pigments in paint. Azo dyes have the basic structure: The unit containing the N=N bond is called the azo group. Azo dyes are commonly synthesized from anilines that have undergone diazotization (an electrophilic intermediate) and other aromatic compounds that contain an electron rich aromatic ring (a nucleophilic counterpart). These aromatic precursors were found in coal tar, a crude material that is obtained from distilling coal. The representative reaction scheme is shown below. Aromatic compound with -OH Diazotization reaction Coupling reaction Aromatic amine Azo dye preparation involves two parts: The first part is the diazotization reaction where an aromatic amine is converted to a diazonium salt. The second part is the coupling reaction where the diazonium salt is coupled with an aromatic compound containing an activating group such as -OH, -NR2. For more information regarding the chemistry of the azo dye preparation, read textbook McMurry 9th edition Chapter 24-8 Diazonium salts (page 812) and Diazonium Coupling Reactions page 815. 1. Watch this video for the preparation of an azo dye https://youtu.be/UDYquCFQJJE 2. What aromatic amine was used in the diazotization reaction in this video? Provide the name and structure. 3. What aromatic compound was used in the coupling reaction with the diazonium salt in the video? Provide the name and structure. 1 4. At 1:37 minutes into the video, 10 mL of 1M HCl was added to benzocaine. Explain why aqueous HCl dissolves benzocaine. Use structures in your explanation. 5. Explain why the reaction must be carried out at a low temperature (at ~5℃ in the video)? 6. Write the chemical equation and mechanism for the reaction that occurred when solution A is added to solution B. 2 7. 2-naphthol dissolves well in NaOH solution but not in pure water and dilute acids. Why? 8. Write the chemical equation and mechanism for the reaction that occurred when solution C is added to the reaction mixture of A + B. 9. If you are given 1-naphthol instead of 2-naphthol as your coupling compound, what is the structure of the azo dye? 3 10. Fill in the table below. Compound Amount in grams or mL benzocaine NaNO2 1M HCl Product (azo dye) 0.21 g (a) Calculate the theoretical yield of the reaction. (b) Calculate the % yield of the reaction. 11. How would you prepare a different color azo dye from the one shown in the video? Provide a chemical reaction for your azo dye reaction. 4 ...