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Methyl Orange : Organic synthesis

In this video we will be synthesising methyl orange indicator dye Methyl Orange is an azo dye formed by the classic azo coupling reaction between diazotised sulfanilic acid with NN dimethyl aniline. Methyl orange is actually an acid indicator which shows a yellow color in pH more than and red color in pH less than . Materials required Sodium Carbonate anhydrous - 3.6g Sulfanilic acid - 10.8g Sodium Nitrite - 4.5g Concentrated 37% HCl - 15ml NN - dimethylaniline - 7.43ml 10% Sodium hydroxide soln - 90ml Sodium chloride - 30g Synthesis can be achieved by following various steps 1: Prediazotisation step This step involves converting sulfanilic acid into sodium sulfanilate For this purpose 150ml distilled water was taken in a 250ml Erlenmyer flask and 3.6g sodium carbonate was dissolved in it. Next we add 10.8g Sulfanilic acid into this solution On adding ,you see an effervescence and bubbles are seen. This is because Sodium carbonate reacts with sulfanilic acid to form Sodium sulfanilate and CO2 is released. Gently warm the solution to ensure complete reaction(The solution turns clear) Step 2: Diazotisation Add 4.5g sodium nitrite into filtrate, Stir to dissolve it. Now keep it in ice bath to cool. Keep that thing aside. Now take a large 400ml beaker and add 75 ml of crushed ice water. Add 15ml conc.HCl into it with stirring. Be careful with concentrated acid. Make sure that the temperature of this solution is less than 5°C.(Use a thermometer) Now transfer the prepared diazotised sulfanilic acid solution into this slowly with stirring. After stirring for some while we start seeing a white precipitatw which is so fine that it almost looks like a suspension. This is the Diazonium chloride suspension. We dont need to isolate the compound from this because we are directly going to use it as such. Now we move into coupling reaction. We transfer the 7.4ml NN- dimethylaniline into the solution present in it 400ml beaker.Wash the container in which it was taken with 6ml of glacial acetic acid and pour that too into the beaker. Stir for 15minutes. Since NN dimethylaniline is an organic compound and oily in nature is it not soluble in water ,this necessitates stirring which allows the particles to react. On stirring for sometime the color of the compound turns darker and darker and the consistenct becomes thicker and thicker. Finally a thick red precipitate is formed. Now on addinng acetic acid ,dimethylaniline acetate is formed which is a good nucleophile and attack on the diazonium compound occurs in the para position due to hindrance at the ortho position due to bulky Dimethylaniline substituent. Now we start adding the 90ml of 10% Sodium hydroxide slowly with constant stirring. Continue adding the Sodium hydroxide with sittiring until the solution becomes basic. Thus completes the reaction of synthesis of methyl orange. The next step is purification. For that we need to boil the ppt in hot water.Methyl orange is soluble in hot water. So adjust the volume of hot water to completely dissolve the precipitate. Now we can use the 30g Sodium chloride to help induce precipitation of methyl orange. Allow it to cool and we get beautiful golden orange flakes of Methyl orange whicb can be dried and collected. This video has been recorded and edited with much effort and difficulty. Lack of proper equipment and chemicals can make video look unfinished. I request your love and support in donations also. Links below 👇 Support me on patreon   / vibzzlab   Or Support me via paypal https://www.paypal.me/vibzzlab If you have any suggestions on new videos , modification to be done or queries regarding any content or anything you don't understand or complaints regarding any of the contents, You can email me Email id : [email protected] Intro music courtesy Lights by Sappheiros   / sappheirosmusic   Creative Commons — Attribution 3.0 Unported — CC BY 3.0 Free Download / Stream: https://bit.ly/LightsSappheiros Music promoted by Audio Library    • Lights – Sappheiros (No Copyright Music)   Rest of the music Funkorama YouTube free audio library.