Hi
I was doing an organic syntheis. I was supposed to obtain the product as a white powder. Instead, I was getting an yellowish and bit oily and sticky product.
I am giving below the procedure I followed.
I have taken my starting materials in DMF and heated at 70C overnight. After cooling over ice, I filtered the salt formed. I added the filtrate to cold chloroform while stirring. At this stage I can see white deposits floating and settling down, as expected. I tried to Vacuum filter the product using sintered glass funnel and wash it with cold Chloroform. At this stage the product turns little yellowish and also starts to turn oily.
Is it that the product is absorbing moisture during the filtering and washing steps ? Is there anything I am doing wrong? How can I purify my product ? Will recrystallisation help?
Please advise me.
Thank you for your time.
Yes, I too feel that this material is taking up some moisture. I suggest to dry it (with heating) in inert atmosphere.
The origin of color of an organic substance is related to the structure, electronic transition and it depends on several factors, such as the presence of chromophores, auxochromic moieties, solvent, temperature, foreign material interacting or influencing the electronic environments. When something (impurities, reagents, solvents) present with the organic compound that can reduce the electronic band gap for enhancing pi to pi star electronic transitions resulting color in the visible light. if the used solvent for precipitation or recrystallization of the desired product, which can partially or very slightly solubilize resulting sticky product. Therefor, please choose a suitable solvent for recrystallization and dry it in vacuum.
Thank you very much Mr. Abdur for the logical explanation. It is very helpful.
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