Write a formal procedure about the expiremnt ( please note where the procedure i

Question

Write a formal procedure about the expiremnt ( please note where the procedure is starting just write it)

-SYNTHESIS OF A DYE, METHYL ORANGE is the electrophile. Therefore the same rules as for any electrophilic aromatic substitution ap- ply: electron donating groups such as amines, ethers and alkyl groups activate the aromatic contact with the skin should be avoided substrate and are ortho-para directors, hlAvoid breathing the fumes. As a general rule groups such as carboxylic esters and nitro all aromatic amines should be considered as Safety Considerations N.N-Dimethylaniline is quite toxic. Any groups are deactivators and meta directors The first step in an azo coupling is the forma Normal precautions apply to the use of concentrated acids. on of the diazonium ion intermediate, which is formed by reaction of an aromatic amine with nitrous acid. This process is called diazotation. Sodium dithionite slowly decomposes in water Nitrous acid is sodium nitrite and hydrochloric acid. For the rotten egg smell). Some people with asthma reaction in this experiment, the diazoniu of sulfanilic acid has to be formed. However sulfanilic formed in situ by reaction of and forms H,S, which really smells bad (the m ion might be highly sensitive to these chemicals. acid is not soluble in acidic solution, and the medium in this reaction has to be acidic to form the nitrous acid. This problem is circum- vented by dissolving the sulfanilic acid first in alkaline solution by addition of sodium carbon ate. At the beginning of the reaction, when HCI is added, two things will happen: nitrous acid Procedure In a small Erlenmeyer flask, dissolve 0.06 g of sodium carbonate in about S mL of water. Add 0.2 g of sulfanilic acid monohydrate and heat to reflux until it is homogeneous. Cool to room formed in situ and the sulfanilic acid will temperature and add 0.08 g of sodium nitrite and stir until homogeneous. Cool in an ice water bath for 5-10 minutes until the temperature is below 10 °C. Add 0.25 mL concentrated hy precipitate out as a very finely divided precipi tate, which is highly reactive. The diazonium salt of the sulfanilic acid will be formed, which is also insoluble in the reaction medium, but drogen chloride to the solution. The diazoniu again very finely divided. The diazonium ion salt should precipitate as a finely divided whi will react immediately with the highly reactive bresipitate, Keep this solution cold N,N-dimethylaniline to form methyl orange Methyl orange is an acid base indicator: At In a vial or flask, mix 0.14 mL. of N,N-dlimethyl pH > 4.4, methyl orange exists mostly as the aniline with 0.10 ml. of glacial acetic acid. Add yellow negative sulfonate ion, while at pH

Explanation / Answer

Diazonium salt formation

Take 50ml beaker and add 60mg of sodium carbonate into it.
Dissolve sodium carbonate into 5ml water by stirring.
In this solution, add 200mg of sulpanilic acid monohydrate and heat the solution to 100oC till all the compound dissolves and gives you homogenous mixture.
Cool the solution to room temperature
Now add 80mg of sodium niitrate into it and again stirr it to dissolve sodium nitrate completely.
Cool the above solution by placing it in ice bath till the temperature of solution is 10oC.
Then add 0.25ml of concentrated HCl solution.
White coloured solid will start to separate out when solution is cold.
Label it as beaker A.

Azo coupling

Take another 25ml beaker and add 0.14ml of N,N-dimethylaniline and 0.10ml of glacial acetic acid.
Pour this solution slowly and deopwise into solution conained in beaker A with constant stirring.
Make sure the whole mixture must be cool below 5oC using ice bath.
After 10-15 minutes, red coloured compound will start to separate out.
Keep the mixture cool.
Then add 1.5ml of 10% NaOH solution slowly and dropwise.
Continously check pH using pH paper. Add NaOH till the solution becomes basic.

Work up

Reflux the given solution for 10-15 minutes till Methyl orang dissolves.
Then add 500mg of NaCl into the above solution.
Cool the solution to room temperature.
Cool it further using ice bath.
Filter the solid obtained using Buckner funnel.
Give washing of 10% NaCl solution (1ml) to this product.
Dry the product.
Save the product.

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