Chemically Active Extraction

Summary

The video demonstrates the process of chemically active extraction, focusing on acid-neutral and base-neutral mixtures. The procedure involves using diethyl ether to extract and separate unknown compounds, followed by washing with sodium hydroxide or acid, depending on the mixture. The separatory funnel technique is utilized to distinguish between aqueous and organic layers. The organic layer is dried using sodium chloride and calcium chloride, then filtered. The final steps include isolating the neutral unknown compound through steam distillation and precipitating the unknown acid or base for further analysis. Emphasis is placed on accurate documentation in the laboratory notebook.

Takeaways

• 🔬 The laboratory exercise involves performing a chemically active extraction of an unknown compound mixture that is either acid-neutral or base-neutral.
• 📝 It is crucial to record the number of the unknown mixture in the laboratory notebook, whether it's a paper or electronic version.
• 🧪 Dr. Amenta demonstrates the acid-neutral extraction process, which includes mixing the unknown sample with diethyl ether and transferring the mixture to a separatory funnel.
• ⚗️ Ensure the complete transfer of the unknown sample by rinsing the test tube with diethyl ether multiple times to avoid losing any material.
• 🔧 When using the separatory funnel, always close the stopcock before adding any liquids and vent periodically during shaking to release pressure.
• 💧 The extraction involves separating an aqueous layer (bottom) and an organic layer (top), with sodium hydroxide added to react with the acid.
• ❄️ After multiple extractions, the combined aqueous layers are placed in an ice bath for further processing while the organic layer is dried using calcium chloride.
• 🧊 The organic layer is further purified using a saturated sodium chloride wash, and then dried using calcium chloride before isolating the neutral compound.
• 🔥 A steam bath is used to remove the ether from the organic layer due to ether's low boiling point and flammable nature.
• 📝 It is important to check the litmus paper to confirm the solution's acidity and record all details about the unknown mixture in the laboratory notebook.

Q & A

What type of extraction is being performed in the laboratory?

The laboratory is performing a chemically active extraction, specifically either an acid-neutral or a base-neutral mixture extraction, depending on the unknown mixture assigned to the student.

What should students ensure to record before starting the experiment?

Students should ensure to record the number of their unknown mixture in their laboratory notebook, either in a paper copy or electronic version.

What solvent is used to help transfer the mixture from the test tube to the Erlenmeyer flask?

Diethyl ether is used to help transfer the mixture from the test tube to the Erlenmeyer flask.

Why is sodium hydroxide added to the unknown mixture?

Sodium hydroxide is added because the demonstration is for an acid-neutral mixture. It reacts with the acid component to form an aqueous layer.

How can you tell the difference between the aqueous and organic layers in the separatory funnel?

The aqueous layer will be at the bottom, and the organic layer will be at the top. Sometimes it's difficult to see, so placing your hand behind the separatory funnel can help identify the interface.

Why is it important to vent the separatory funnel during shaking?

Ventilation is important to release any pressure that builds up during shaking, preventing any accidents from over-pressurization.

What is the purpose of adding saturated sodium chloride to the organic layer?

Saturated sodium chloride is added to wash and further separate the organic layer from any remaining aqueous components.

Why is solid calcium chloride added to the organic layer?

Solid calcium chloride is added to dry the ether layer by absorbing any water that may still be present.

How can you tell when the ether has completely evaporated during the steam bath process?

You can tell the ether has completely evaporated when there are no more bubbles forming and the mixture stops boiling. Ether has a low boiling point, so once it evaporates, only the unknown liquid with a higher boiling point will remain.

What is the final step for the unknown neutral compound after evaporation of the ether?

The final step is to transfer the neutral unknown into a pre-weighed round bottom flask for storage, ensuring that no liquid is lost during the transfer.