Question: A student dissolved 0.30 g of a crude product in 10.5mL (the minimum amount required) of ethanol at 25 degrees C. He cooled the solution in an ice-water bath for 15 minutes and obtained beautiful crystals. he filtered the crystals on a Hirsch funnel and rinsed them with about 2.0 mL of ice-cold ethanol. After drying, the weight of the crystals was found to be 0.015 g. Why was the recovery so low?

Question

Question: A student dissolved 0.30 g of a crude product in 10.5mL (the minimum amount required) of ethanol at 25 degrees C. He cooled the solution in an ice-water bath for 15 minutes and obtained beautiful crystals. he filtered the crystals on a Hirsch funnel and rinsed them with about 2.0 mL of ice-cold ethanol. After drying, the weight of the crystals was found to be 0.015 g. Why was the recovery so low?

My answer: The problem is that the solvent dissolves the crude product at room temperature. This makes is highly likely that much of the product remains in solution. It's best to find a solvent that dissolves at boiling point and gives it back at room temperature?

Thanks for checking this.

Sheryl

It looks good to me. I answered a question for Lindz (about half a page down from this post) regarding addition of Br2 and Cl2 to a double bond. Look at them and see if you agree with them. My friend in town will be out of town tomorrow or I would have him look at them. He would know the answers in a flash.

Answer 1

I'm glad you found my answer helpful, Sheryl! As for the other question you mentioned, unfortunately, I cannot browse or review any specific posts or answers from Lindz or your friend in town. However, if you have any other questions or need further assistance, I'll be more than happy to help!

Answer 2

Thank you for your feedback! It seems like you are referring to a different question or conversation. Is there anything else I can assist you with regarding the low recovery of the crystals?

Answer 3

Thank you for your response, Sheryl. It seems like you have provided a reasonable explanation for the low recovery of the crystals. The fact that the solvent used, ethanol, dissolves the crude product at room temperature suggests that a significant amount of the product remained in solution rather than crystallizing out.

To improve the recovery, it is indeed advisable to find a solvent that can dissolve the crude product at its boiling point but precipitate it out when cooled to room temperature. This approach, known as "recrystallization," is commonly used to purify solid compounds by taking advantage of differences in solubility at different temperatures.

By selecting a suitable recrystallization solvent with a higher boiling point than ethanol, it is possible to dissolve the crude product at elevated temperatures to ensure complete dissolution, and then cool the solution slowly to allow the desired compound to crystallize while impurities remain in solution. This can potentially lead to a higher recovery of pure crystals.

However, it is important to note that without more specific information about the nature of the crude product and its solubility characteristics, it is difficult to provide a definitive explanation for the low recovery.