Synthesis of methyl orange PDF

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lab report for the synthesis of Methyl orange...

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Synthesis of Methyl Orange Author's Name Institutional Affiliation Course Name and Number Instructor's Name Assignment Due Date

2 Synthesis of Methyl Orange Abstract The aim of this lab was to make methyl orange, a synthetic dye. Methyl orange is a dye made by combining diazonium ions with aromatic structures in a synthesis reaction. Aromatic N+Naromatic, azo group is the fundamental structure of dyes. A coupling reaction between diazonium ion and N, N-dimethyl aniline was used to make methyl orange during simple conditions. Under specific elements, the dizonium ion is made from sulfanillic acid monohydrate and N, Ndimethyl aniline. After adding sodium hydroxide, basicity was determined using pH paper, which revealed a light blue color, indicating a pH value of 10. With a percent error of 28.46 percent, the product yield was estimated to be 71.53 percent, indicating that methyl orange was produced reasonably. Introduction The diazo coupling reaction seen between diazonium selling of sulfanilic acid and N, Ndimethylaniline produces methyl orange. The red acid form of methyl orange is the first result of the coupling reaction, which is later converted to orange sodium salt, also known as methyl orange. Fabrics are dyed, and chromophores, which are organic molecules that absorb light, are used to color them.

3 Results/discussion Experiment 7: Methyl Orange Synthesis (Data Sheet) Part 1: Reactions execution : In a 25 mL Erlenmeyer flask, 0.061 g of anhydrous sodium carbonate is soluble in 5 mL water. The mixture was heated with 0.182 g of sulfanilic acid, which allowed the solids to dissolve. After allowing the mixture to cool to room temperature, 0.083 g sodium nitrite was applied, stirring constantly. In an ice bath, the mixture was then poured. Part 2: Running the reaction: In an ice bath, the suspension created in Part 1 was installed. In a 3-mL conical vial, 0.15 mL of N, N-dimethylaniline and 0.10 mL of glacial acetic acid were combined. This solution was dropped into the suspension made in Part 1 in a drop by drop fashion. When the mixture was stirred, a red precipitate formed. After 10 minutes, 1.5 mL of 10% NaOH was added drop - wise to the mixture, which was stirred for 10 minutes until pH-value was tested (pH=8-9). Product isolation: The suspension was brought to a gentle boil, then 0.5 g of solid NaCl was applied. After cooling to room temperature, the solution was put in an ice bath. Filtration on a Buchner funnel was used to separate the solid. 5 mL cold sodium chloride solution was used to remove the remaining solids. To dissolve the substance, the solids and filter paper were put in 15 ml of boiling water. Before putting the mixture in an ice bath, let it cool to room temperature (15 minutes) Vacuum filtration is used to separate the solids. Enable the product to dry before weighing it. Product

4 characterization: 0.172 g of the product UV-Vis spectrum (c=5.2*10% M, water, pH=2 and pH=6) 2,213 2,000 Solvent water 1,000 -0,01$ 400,0 500,0 700,0 800,0 600,0 Wavelength (m.) Pick Peak Pick No. Wavelength (nm.) 464.50 Abs. 1,0647 No. Wavelength (m. 1 508,50 Abs 1, 7520 H-NMR (D20) PI 0.41 0.16 Conclusions and summary N, N-dimethylaniline, and sulfanilic acid were used to make methyl orange. The diazonium salt of sulfanilic acid was generated using sodium nitrite. After the first step, the solution was treated with hydrochloric acid to produce a dizonium salt precipitate. Following a coupling reaction between a diazonium salt and N, N-dimethylaniline, light orange-colored methyl orange precipitates were formed. When hydrochloric acid with a pH of 3 was added, the color changed to red, and when sodium hydroxide was added, the color changed to orange. The methyl range had a theoretical yield of 0.3872g, but the real yield was 0.2770g. The percent yield was found to be 71.53 percent. Experimental section The diazotization reaction must be carried out in an acidic solution. Sulfanilic acid, on the other hand, is insoluble in acid. To address this problem, the sulfanilic acid should be first dissolved in a sodium carbonate aqueous solution. After that, sodium nitrite is added to the basic solution. The solution is then cooled before being acidified using hydrochloric acid. Sulfanilic acid is diazotized as soon as it leaves the solution, resulting in a finely divided white precipitate of the diazonium salt of sulfanilic acid. In the solution where it was precipitated, this diazonium salt is allowed to react instantly with dimethylaniline.

5 Since the azo linkage (-N=N-) connects two aromatic rings, resulting in an extended conjugated structure that absorbs light in the visible field, azo compounds are sometimes brightly colored. Methyl orange is a common acid-base indicator, and when the pH varies from 3.2 to 4.4, the color changes. Methyl orange is red in acidic solutions with a pH below 3.2, with a maximum wavelength of 520 nm. Methyl orange is yellow in basic solutions, above pH=4.4, with a max=460 nm. Spectra section

UV-Vis spectrum (c=5.2*10-5 M, water, pH=2 and pH=6) UV-vis spectra of methyl orange (concentration. 5.2 x 10-5 M) in alkaline and acidic forms in water IR, 1H NMR:

6 Due to inadequate drying of the product, a broad absorption near 3400 cm-1 (O-H from water) but several absorption bands in the region 1400 - 650 cm cm-1 (S=O stretching) can be seen in the IR spectrum. At 1420 cm-1, N=N stretching vibration is also noticeable.

7 Post Lab questions

1. Provide a mechanism for this coupling reaction. In the presence of nitrous acid, sulphanilic acid is converted into sodium salt of paminobenzene sulphonate, which then undergoes a diazotization reaction to form diazonium chloride salt. In aqueous solution, the diazonium chloride ionizes, yielding sodium, chloride, and the internal salt. When N, N-dimethylaniline hydrochloride is added to the internal salt, electron aromatic substitution occurs, and methyl orange is produced. Why does this reaction lead to a coupling at the para position of the dimethylamino group? When a primary aliphatic amine reacts with nitrous acid, it forms an unstable diazonium salt that loses N2 to form a carbocation. The carbocation can then (1) lose a proton to form an alkene, (2) react with a nucleophile, or (3) rearrange, before repeating steps 1 and 2. (2). Dimethylaniline is the nucleophile in this case. The bulky dimethylamine substituent causes steric hindrance in the ortho position, so the attack is in the para position. 3.In the formation of helianthin, after the coupling reaction has occurred, a proton is transferred from the dimethylamino group to one of the azo nitrogens, leading to a more stable product. Why is this product more stable than the first one, when the proton was on the dimethylamino group?

8 The lower the energy, the more stable the final product, which is more stable than the original product. The proton is moved from the dimethylamino group to the azo group linkage as a result of the Aldol Condensation. Diazonium salts or diazonium compounds are a class of organic compounds that share a functional group.

4 A colored compound absorbs light in the visible range. The light, which is not absorbed, gives the compound the color, which we see. What colors are absorbed by the acidic and basic form of methyl orange?

In an acidic medium, methyl orange turns red, while in a basic medium, it turns yellow. 5. Extra credit: Why does the 1H-NMR spectrum show a large signal at =4.65 ppm despite the use of D2O as solvent? Depending on the solvent used, water signals appear at various frequencies in 1H NMR spectra.

9 References Astolfi, D. L., & Mayville Jr, F. C. (2003). Synthesis of methyl orange using ionic liquids. Tetrahedron Letters, 44(51), 9223-9224....