Test for Carboxylic Acids

Summary

This educational video explores carboxylic acids, organic compounds found in citrus fruits and vinegar, and demonstrates various tests to identify them. It categorizes acids into aliphatic and aromatic, showcasing examples like formic, acetic, benzoic, citric, and tartaric acids. The video conducts tests including the litmus test, sodium bicarbonate reaction, ester formation, and a fluorescein test specific to dicarboxylic acids. It also acknowledges the support of Patreon backers in facilitating these experiments.

Takeaways

• 🔬 Carboxylic acids are organic compounds with the COOH functional group.
• 🍇 Carboxylic acids occur naturally in citrus fruits like grapes and green apples.
• 🧪 Vinegar is a dilute solution of acetic acid, which is a type of carboxylic acid.
• 📦 The video presents samples of carboxylic acids, including formic acid and acetic acid.
• 🌿 Aromatic carboxylic acids like benzoic acid are also discussed, with a link to a synthesis video in the description.
• 🍊 Citric acid is highlighted as commonly found in grocery stores, and tartaric acid is noted in tamarind fruit.
• 🧪 The litmus test is demonstrated to show the acidic property of carboxylic acids, turning blue litmus paper red.
• ⚗️ The sodium bicarbonate test produces a carboxylate salt and carbon dioxide, observed as effervescence.
• 🍸 The ester test involves a reaction between carboxylic acid and alcohol to produce esters with a fruity smell.
• 🌈 The fluorescein test is a special confirmatory test for dicarboxylic acids, resulting in a red color and green fluorescence under UV light.
• 🙏 The video creator thanks their Patreon supporters for helping to fund the materials needed for these experiments.

Q & A

What are carboxylic acids?

Carboxylic acids are organic compounds characterized by the presence of the -COOH functional group. They occur naturally in citrus fruits and are exemplified by acetic acid found in vinegar.

How are carboxylic acids classified?

Carboxylic acids are classified into aliphatic and aromatic acids based on their structure.

What is the difference between aliphatic and aromatic carboxylic acids?

Aliphatic carboxylic acids are those with an open chain structure, like formic and acetic acids. Aromatic carboxylic acids have a benzene ring in their structure, such as benzoic acid.

What is the purpose of the litmus test in the context of carboxylic acids?

The litmus test is used to demonstrate the acidic property of carboxylic acids. When carboxylic acid is dropped onto blue litmus paper, it turns red.

How does the sodium bicarbonate test work with carboxylic acids?

In the sodium bicarbonate test, carboxylic acids react with sodium bicarbonate to produce a carboxylate salt and release carbon dioxide, which is observed as effervescence.

What is the ester test and how is it performed?

The ester test involves reacting a carboxylic acid with an alcohol in the presence of concentrated sulfuric acid and heat to produce an ester, which has a fruity smell. This is done by mixing the acid with alcohol, adding sulfuric acid, and then heating the mixture.

What is the purpose of the fluorescein test for carboxylic acids?

The fluorescein test is a confirmatory test for dicarboxylic acids. It involves the reaction of the dicarboxylic acid with resorcinol and concentrated sulfuric acid to form fluorescein, which shows green fluorescence under ultraviolet light.

Why is the fluorescein test specific to dicarboxylic acids?

The fluorescein test is specific to dicarboxylic acids because it relies on the reaction of two carboxylic acid groups with resorcinol to form the fluorescent compound fluorescein.

What precautions are taken during the ester test?

During the ester test, the mixture is not directly sniffed to avoid inhaling the volatile compounds. Instead, the air above the beaker is gently wafted towards the nose to detect the fruity smell.

How is the alkalinity of the solution checked after the fluorescein test?

The alkalinity of the solution after the fluorescein test is checked using red litmus paper, which turns blue in an alkaline solution.

What is the final observation when testing for fluorescein under normal white light?

Under normal white light, the presence of fluorescein shows a green fluorescence in the reflected light, and the transmitted light appears deep red.