Sandmeyer isatin synthesis - tarry material?

In summary, the conversation is about a project involving the synthesis of isatins using the Sandmeyer methodology. The speaker is having trouble with the condensation reaction due to the formation of a tarry material, which affects the yield and purity of the final product. They have tried following a synthesis protocol but still encountered the same issue. They are seeking advice on preventing the precipitation of aniline sulfate during the reaction and are using TLC to monitor the progress. The reaction takes place in a roundbottomed flask at 60-80°C for 2-2.5 hours with magnetic stirring. The speaker is also asked about the aniline solution used and how long it was heated before boiling, the color of the aniline, and
  • #1
teenspeerit
1
0
Hey everyone!

I am currently working on a project regarding the synthesis of variously substituted isatins using the Sandmeyer methodology, involving the condensation of chloral hydrate, hydroxylamine and substituted aniline (in this case the 4-ethylaniline) to nitrosoacetanilide with following cyclization under strongly acidic conditions to give the isatin.

640px-Synthesis_of_isatin.png


However, I seem to be stuck on the condensation reaction due to the prevalent formation of a tarry material which I have been unable to wash off, and which seems to cause problems in the cyclization-step, giving lower yields of sticky, impure product. If I follow the synthesis described in the following preparation: http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv1p0327, I get an immediate formation of insoluble creme/brownish crystals upon addition of the aniline, which i assume is the aniline sulfate. However, after heating of the reaction mixture, the tar seems to form on/in the crystals. How can I prevent the precipitation of the aniline sulfate, to allow the acetanilide to precipitate, and could the precipitation of the aniline sulfate be the cause of the tarry compound?

The reaction takes place in a roundbottomed flask at 60-80°C (oil bath + internal thermometer) with magnetic stirring for 2-2,5 hours. I use TLC to moniter the reaction (EtOAc/heptane 1:1) which consistently shows the formation of 2 products with the complete conversion of the aniline.
 
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  • #2
Describe the aniline solution you used and how long did you heat it before it boiled? What color was the aniline you used? Did you use the anhydrous sodium sulfate or the hydrate?
 
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What is the Sandmeyer isatin synthesis?

The Sandmeyer isatin synthesis is a chemical reaction used to synthesize isatin, an organic compound commonly used in the production of dyes, pharmaceuticals, and other industrial products.

What is tarry material?

Tarry material is a dark, sticky substance that is often produced as a byproduct during the Sandmeyer isatin synthesis. It is composed of various impurities and unreacted starting materials.

Why does tarry material form during the Sandmeyer isatin synthesis?

Tarry material is formed due to the presence of impurities in the starting materials, which can undergo side reactions during the synthesis process and result in the formation of tarry material. Additionally, the reaction conditions and temperature can also play a role in the formation of tarry material.

How can tarry material be removed from the final product?

Tarry material can be removed from the final product through various purification methods, such as recrystallization, distillation, or column chromatography. These methods help to separate the tarry material from the desired product.

Are there any potential hazards associated with tarry material?

Yes, tarry material can be potentially hazardous due to the presence of impurities and unreacted starting materials. It is important to handle tarry material with caution and use proper safety precautions, such as wearing protective gloves and eyewear, when handling it.

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