Making Formic Acid

Summary

In this video, the process of synthesizing formic acid from oxalic acid is demonstrated. The procedure involves heating oxalic acid dihydrate with glycerol as a catalyst, followed by distillation to separate the formic acid from byproducts. The reaction is driven by an excess of water, and fractional distillation is used to purify the formic acid, removing impurities like acrylonitrile and allyl alcohol. The final product is a crude form of formic acid, which is then distilled to a purity of 77.5% azeotropic formic acid. The video emphasizes the synthesis process while briefly touching on purification techniques.

Takeaways

• 😀 Oxalic acid is the simplest dicarboxylic acid, and when decarboxylated, it forms formic acid.
• 😀 Glycerin (glycerol) is added as a catalyst to the reaction of oxalic acid to form formic acid.
• 😀 The reaction setup involves heating oxalic acid and glycerin to 125°C in a three-neck boiling flask for a simple distillation.
• 😀 The thermometer should be placed in the reaction mixture to monitor the temperature of the reaction, not the vapor phase.
• 😀 The target reaction temperature is 110°C; temperatures above this can lead to toxic byproducts like acrylonitrile and allyl alcohol.
• 😀 Formic acid shares its name with a type of wood ant that uses formic acid for self-defense.
• 😀 To drive the reaction forward, 110 grams of additional oxalic acid dihydrate is added to provide more water and oxalic acid.
• 😀 The reaction can be repeated multiple times by adding more oxalic acid and glycerol to generate more formic acid.
• 😀 After heating, the crude mixture of formic acid and byproducts undergoes fractional distillation to separate impurities.
• 😀 During fractional distillation, water distills at 100°C, and a 77.5% azeotrope of formic acid and water distills at around 105°C.
• 😀 The final product obtained is 77.5% azeotropic formic acid, and while the video doesn't focus on purity, it can be titrated if desired.

Q & A

What is the main reaction taking place in the script?

The main reaction is the decomposition of oxalic acid dihydrate to form formic acid through a decarboxylation process, with the addition of glycerin as a catalyst.

Why is glycerin added to the reaction mixture?

Glycerin is added to act as a catalyst for the reaction, helping drive the decomposition of oxalic acid and facilitate the production of formic acid.

What temperature is the reaction heated to, and why is this temperature significant?

The reaction is heated to 125 degrees Celsius. This temperature is important because it ensures the reaction occurs at the target temperature of 110 degrees Celsius, preventing the formation of toxic byproducts like acrylonitrile or allyl alcohol.

What is the purpose of placing the thermometer in the reaction mixture instead of the vapor phase?

The thermometer is placed in the reaction mixture because it is more important to monitor the temperature of the mixture itself rather than the vapor phase to ensure the reaction occurs at the correct temperature.

What are the potential toxic byproducts of this reaction, and why should they be avoided?

The potential toxic byproducts are acrylonitrile and allyl alcohol. These should be avoided as they are harmful and could contaminate the product.

How is the reaction continued after the initial distillate shows low formic acid content?

To continue the reaction, additional oxalic acid dihydrate is added to provide more water and oxalic acid, ensuring the reaction proceeds and more formic acid is produced.

Why does the glycerol act as a catalyst and not get used up in the reaction?

Glycerol acts as a catalyst because it facilitates the reaction without being consumed in the process. It is regenerated at the end and does not participate directly in the decomposition of oxalic acid.

What is the role of fractional distillation in this process?

Fractional distillation is used to separate the crude formic acid from toxic byproducts and water, allowing for the purification of formic acid.

Why is the distillation process carried out in stages at specific temperatures?

The distillation is carried out at specific temperatures to separate the components based on their boiling points. Water distills first at around 100°C, and a 77.5% azeotrope of formic acid and water distills at around 105°C. Impurities are discarded, and pure formic acid is collected afterward.

What is the final product obtained from the process, and how much was produced?

The final product obtained is formic acid. Approximately 125 milliliters of formic acid is produced in this reaction.