Troubleshooting: Workup

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Workup / Workup Formulas for Specific Reagents

Problem (Workup Nightmare #1): Upon combination of organic and aqueous solutions, a gooey or insoluble precipitate appears, which floats between the two layers and obscures the border.

Solution: Keep washing with water until most of the goo is removed. Then use copious drying agent, and with luck, the goo will be absorbed and you will be able to filter it away.

Problem (Workup Nightmare #2): When an aqueous solvent is added to the diluted reaction mixture, an emulsion forms. All efforts to resolve the layers fail, your solution has swollen to gargantuan proportions, and you can't find or can't lift a separatory funnel large enough to hold it

Solutions:

Problem (Workup Nightmare #3): During Acid/Base Workup, the expected precipitate does not form.

Solution: See Acid/Base Workup.

Problem (Workup Nightmare #4): Upon addition of aqueous bicarbonate, the organic layer becomes a graceful fountain, coating the inside of your fume hood.

Solution: When you repeat the procedure, add aqueous bicarbonate carefully, shake gently, and vent the separatory funnel often.

Problem (Workup Nightmare #5): Addition of aqueous solution to your black organic reaction mixture leads to a uniform black mixture. The solution in the addition funnel is opaque, and you can't see the border between the organic and aqueous layers.

Solution: Try adding ice, which will float on the water, between the layers.

Problem (Workup Nightmare #6): The aqueous solution you use to wash the organic layer turns yellow, orange, brown or pink- the first ten times you try it.

Solution: If the color is caused by excess halogen reagent from your reaction mixture, try washing with sodium thiosulfate. The solution should become instantly clear- if it does not and you still suspect halide, try stirring vigorously in an Erlenmeyer for 10-15 minutes to complete the reduction of halogen molecules.

Problem: (Workup Nightmare #7): After workup, you can't find your product.

Explanations and Solutions:

*If your problem is not on this list, post it on Q & A!*