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During the isolation and purification of caffeine, the water was allowed to cool to room temperature...

During the isolation and purification of caffeine, the water was allowed to cool to room temperature before extraction with methylene chloride. Why was this done, and what would happen if this was not done?

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Answer #1

The main reason is safety, methylene chloride is volatile liquid with very low boiling point of 39.6 °C. Which means that shaking a hot water solution with methylene chloride will make methylene chloride to vaporize off, again it will increase the pressure in the separatory funnel, and chance of explosion.

The other reason is the solubility in hot water, even though caffeine has very low solubility in cold water, it has moderate solubility in hot water, hence extraction at warm condition will not be complete with methylene chloride.

So if the extraction is not done at cold, extraction will not be complete, and loss of caffeine in water.

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