How to Make Anhydrous Oxalic Acid Using Azeotropic Distillation

TL;DR

To make anhydrous oxalic acid, use azeotropic distillation with toluene to effectively remove moisture without sublimating the acid. The Dean-Stark apparatus allows for separation of water from the mixture, resulting in nearly theoretical yields of dry oxalic acid suitable for chemical reactions.

Transcript

Hey guys. Today we're gonna be making some anhydrous oxalic acid, but the method that we use today is a little bit special. Normally, the easiest way to dry a powder is to just put it into the oven, but the problem with oxalic acid is that it very easily sublimates at elevated temperatures. When something sublimates, it converts directly from the ... Read More

Key Insights

• ✋ Oxalic acid easily sublimates at high temperatures, requiring a specialized drying technique.
• 💦 Azeotropic distillation is a method commonly used to remove water from organic compounds.
• 💦 The Dean-Stark apparatus is a valuable tool for separating water from mixtures in distillation processes.
• 🤢 An excess of toluene is used to ensure the smooth operation of the stir bar during mixing.
• 🙂 Oxalic acid turns slightly pink after washing with DCM (dichloromethane), although the color is not significant.
• 👻 Evaporating the oxalic acid in a controlled manner allows for the removal of most of the DCM.
• ❓ The final product is anhydrous oxalic acid, which can be used for various chemical reactions.

Questions & Answers

Q: Why is it difficult to dry oxalic acid using conventional methods?

Oxalic acid sublimates at elevated temperatures, so using an oven would result in the vaporization of the acid and crystal formation in the oven.

Q: What is azeotropic distillation?

Azeotropic distillation is a technique that involves forming a mixture with a selected solvent (in this case, toluene) that can dissolve the water present in the oxalic acid, allowing it to be removed without vaporizing the acid itself.

Q: What is the purpose of the Dean-Stark apparatus in this process?

The Dean-Stark apparatus is used to separate water from the mixture by condensing the vapor and allowing it to flow back into the flask while the water collects separately.

Q: Can the toluene used in the process be reused?

The toluene used in the process can be reused for drying more oxalic acid but should not be used in new reactions due to possible contamination with a small amount of oxalic acid.

Summary & Key Takeaways

• Oxalic acid easily sublimates at high temperatures, making it difficult to dry conventionally in an oven.

• Azeotropic distillation is a technique used to dry oxalic acid by forming a mixture with toluene.

• The Dean-Stark apparatus is used in the distillation process to separate water from oxalic acid.